A power transmission apparatus includes a drive shaft, a driven shaft, a first transmission device, a first one-way power transmission mechanism, a second transmission device, a second one-way power transmission mechanism, and a controller. The first transmission device is to change power of the drive shaft. The first one-way power transmission mechanism is to transmit power changed by the first transmission device only in one direction to the driven shaft. The second transmission device is to change power of the driven shaft. The second one-way power transmission mechanism is to transmit power changed by the second transmission device only in one direction to the drive shaft. The controller is configured to change ratios of the first transmission device and the second transmission device. The controller is configured to make the ratio of the first transmission device larger than the ratio of the second transmission device.