To provide a midsole for sport shoes whose structure is improved in durability at cushion hole forming portions by preventing the cushion hole forming portions in the midsole from flattening, and is improved in bending properties of a front section by enhancing a flexural rigidity of a middle section.

The midsole is provided with an upper midsole 3 made of a soft elastic member which extendingly provided from a heel section to the front section of the shoe, lower midsoles 4, 5 made of the soft elastic member which are arranged in the heel section and the front half section beneath the upper midsole of the shoe, and a first and a second corrugated sheets 6, 7 which are interposed face-to-face between the upper midsole 3 and the lower midsoles 4, 5. Through-holes 10, 11 formed by each corrugated shape face of the first and second corrugated sheets 6, 7 are disposed in the heel section and the middle section respectively. A cross-sectional shape of the through-hole 11 is formed in an oblong cross-sectional shape.