PURPOSE: To provide an air-driven wiper device with air applied as drive source.

CONSTITUTION: Cylinder rods 10, 11 are provided in sector cylinders 7, 8 symmetrical with respect to an output shaft 9 and forming a viper motor 2, and a viper arm 12 is fitted to the output shaft 9. The cylinder rods 10, 11 divide the internal space of the sector cylinder 7, 8 respectively into air chambers 7a, 7b and 8a, 8b. Inflow ports 13-16 are provided to lead in air, and a direction change-over valve 19 is provided to changeover-forming air supply passages. Because of being air-driven, there is no heating of the motor itself, nor is speed change mechanism or the like used. Structure is thereby simple, durability is improved, and mechanical noise can be suppressed.