An air cylinder includes a cylinder, a piston rod, a piston, and a controller. The piston rod has one end disposed in the cylinder and the other end protruding from the cylinder. The piston is provided at the one end of the piston rod and moves the piston rod by moving in the cylinder. The controller supplies gas into one of a space, which is a space in the cylinder directed on the piston rod side with respect to the piston, and a space, which is a space in the cylinder opposite to the space with respect to the piston, and sucks gas from an interior of the other of the spaces.