A ventilating structure for a shoe is provided, which contains a duct member containing a number of air ducts communicating with a plurality of through holes at the sole's rim, a first pad member having a plurality of through holes on top of the duct member, a semi-spherical bubble member fixedly attached to the top of the first pad member covering at least a through hole of the first pad member directly above an air duct of the duct member, and a second pad member on top of the first pad member having a number of through holes and a bulged section accommodating the bubble member. As a user walks on a shoe of the invention, the bubble member, like a pump, undergoes intermittent compressions and releases by the user's foot, causing warm and humid air to be expelled out or fresh air to be drawn inside of the shoe quickly and periodically.