PURPOSE: To effectively restrict hydroplaning during cornering operation, in the case of a flat tire having an annular recession formed by wholly recessing the cross directional center part of a crown part inward in the radial direction.

CONSTITUTION: If an annular recession 35 is displaced in a waveform in the cross direction of a crown part 15, the annular recession 35 is partly placed in the rotational outside from the cross directional center part (the tread area is increased during the cornering operation), and drain is performed at this part. Moreover, it becomes hard that water enters the tread because a place where the dynamic water pressure becomes highest during cornering operation is continuously fluctuated in the cross direction.