The present invention relates to a device for collecting body fluids including (a) a fluid receiving part including a fluid receiving space in which an internal low pressure less than an external atmospheric pressure is formed; (b) a fluid collection part including a hollow microstructure connected to form an open system with the fluid receiving space of the fluid receiving part; and (c) a microstructure hollow barrier for blocking the hollow of the microstructure to maintain the internal low pressure formed in the fluid receiving means.