The present invention relates to a chain loading device and a passenger conveyor and a chain elongation detection method, and provides a chain loading device and a passenger conveyer and a chain elongation detection method that can detect the elongation of a chain without using a dedicated appliance. The chain-mounted device according to the embodiment includes a motor, a first sprocket, a chain, a second sprocket, an inverter, and a controller. The controller performs vector control on the motor and the inverter, and calculates an elongation amount of the chain based on a torque component current that is an element of the vector control.