It means both, and yes it depends on the context.
Yo no creo en el amor-I do not believe in love
¿Iras a la fiesta esta noche? -No creo- - Will you go to the party this night?- I don't think so
2016년 11월 4일
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Ayúdame*
Could be both :V
It depends on the context but I think it's more usual to translate it like "I don't believe".