An improved structure of ventilating insole, which is composed of a shoe-shaped lower insole, an air permeable layer (cloth or leather) in shoe-shaped and a sponge is placed between the lower insole and the air permeable layer, its features are as follows, a concave trough with casing is set in the central part of the lower insole when molding it in one-body-type, an elastic, porous sponge which is trough-shaped in equal thickness is placed onto the trough of the lower insole, then casing around trough is glued to the air permeable layer with air inlet ports at the heel and air outlet ports at the toe portions, a ventilating insole is then finished. Such an insole provides for pumping cool air into the interior of the shoe as a result of the normal walking action, thus, the shoe can keep ventilating properly.