Antique usually is an older item within the last few centuries. Artifact is much older and used a lot for archaeology, anthropology, paleontology, etc.

Here is an example of use. "I love to visit Essex because it has so many antique shops. I have my living room furnished with antique furniture. I picked up that wonderful mirror there. Isn't the frame beautiful?" There is no such thing as an "artifact shop." As a matter of fact, it may be illegal to sell them. The word "artifact" is associated with the words "museum," "anthropology," and "archaeology." The word "antique" is associated with the words "beauty," "craftsmanship," "collector," and "valuable." Artifacts may or may not be beautiful. They are interesting because they are characteristic of a culture or a civilization. A century from now, when we control computers by thought, computer mice will be "artifacts." You will go to a museum and there will be a display case with a hundred different computer mice in them. This one is old and scratched up but it is important because it is a rare example of a one-button mouse. This one is small, green, and in the shape of a frog. This shows us that in this culture, mice were used by children. You can see that the older mice have cords attached to them, while the newer ones are wireless. Some of them may be beautiful, or at least "elegant" in design, but they are all artifacts of early 21st century civilization.

An English dictionary (one language) can be helpful here. "Antique" always means old, and usually means something that is valued or valuable because it is considered fine and beautiful. An "artifact" means something made by hand, usually a tool, weapon, or ornament, and often of archeological interest. I've made an image. The top row shows the kind of thing called an "antique:" an antique auto, an antique chair, and an antique book. The bottom five images are "artifacts," keys to the culture of a civilization. They tend to be interesting, whether or not they are particularly beautiful, and they tend to be useful in daily life. Here we see two arrows made of chipped flint; a plow; a butter churn; a travois; and--the only one that isn't useful--a corn-husk doll.

Antiques are old household objects or furniture, usually useful and of value. "Artifact" is simply "something made". It is a very broad concept, so it is hard to state a precise definition. An artifact doesn't have to be intentionally made by a human. Often, an artifact is spurious in some sense - something found or unexpected or a byproduct or leftover of some other process, activity, or society. Nor does an artifact even need to be an object. For instance, a photograph may contain some unexpected discoloration or distortion that the photographer did not want or expect. Such errors in the photo are considered to be "artifacts" of the photographic process.

An antique is an older item that people like to collect for various reasons. It could be because of the value, because of the older look and feel, because of the nostalgia, etc. But yes, they are always man-made items. An artifact is better described as an old item with historical significance. Something that has a lot of cultural or historical meaning. These can be man-made or natural items. It's usually used to refer to an object that has been rediscovered such as archeological finds.