To induce ventilation inside a shoe to lessen the sweatiness of a foot and prevent athlete's foot developing by providing an inside sheet with a flat pump equipped with an induction valve, an exhaust valve and a helical compression spring, and by walking with such inside sheets in the shoes.

When a person walks in shoes, the shoe heel rises and develops a space between the sole and the heel bringing a helical spring 5 into action, with the result that the capacity of a flat pump 2 increases and air is inhaled by way of an induction valve 3. When the heel lands, the weight of the person pressed down the flat pump 2, and the air inside the flat pump is pushed out by way of an exhaust valve 4 and led toward the toe through an air duct 6. Therefore, the air inside the bottom of the shoes shifts and ventilation is performed. In this case, a vinyl sheet is used as material for an inside sheet 1, and an elastic, adhesive crude rubber sheet is used for the induction valve 3. A polyvinyl chloride tube is used as the exhaust valve 4 with one end of it squashed. A thin plate of stainless steel is shaped into a helix and used as a helical spring 5.