To facilitate usage by arranging respective structural portions with good balance.

This air compressor 1 is provided with cylindrical hollow air tanks 2, 2 which is arranged parallel to each other and connected by stays 3, 3 and so on, and the lower surface of the longitudinal front and rear ends of which legs 4, 4 are fixed respectively. On the medial portion of the air tanks 2, 2, a compressor main body 6 with a motor is arranged parallel to the air tank 2 and at the portion slightly higher than the air tank 2. Further, on the under surface of the front and rear ends of the air tank, a pair of cylinders containing pistons which is reciprocated by the rotational motion of the motor 5 through a crank mechanism are disposed to be downwardly projected respectively.