Abstract: A seat air-conditioning device is applied to a seat and includes a cushion material, an outer cover, a ventilation hole and a surface groove. The cushion material supports a back or buttocks of an occupant seated on the seat. The outer cover covers the cushion material and has perforation holes. The ventilation hole is formed at a portion of the cushion material opposed to the back or the buttocks of the occupant seated on the seat. The ventilation hole is configured to suction or blow air. The surface groove is formed at a portion of the cushion material which is adjacent to the outer cover. The surface groove is communicated with the ventilation hole and extends from the ventilation hole in a direction away from a location of the cushion material, at which a center of the back or a center of the buttocks of the occupant is placed.