The invention relates to a vacuum pump for bottles, which is particularly suitable for wine bottles which have been opened but not completely consumed. The inventive pump consists of a support (1) which can be connected to the neck (4) of the bottle and which comprises an inner constriction (2) that rests on the mouth (3) of said bottle. The aforementioned constriction forms the support and the head (7) of a stopper (8) which penetrates the mouth (4) of the bottle and which is solidly fixed thereto. Moreover, the invention also comprises a cover (19) which can be moved axially in relation to the support (1) and which forms a variable-volume chamber (22) along with said support and the head (7) of the stopper. According to the invention, a unidirectional valve (11-14-16) is formed in the stopper (8) and a second unidirectional valve (20-21) is formed between the support (1) and the cover (19) such that, when the chamber (22) increases, air is drawn from inside the bottle and, when the chamber decreases, said air is released to the exterior.