Abstract: A testing device is provided for checking the resistive force of a retarder installed on the rail of a railway track for reducing the speed of a railcar rolling along the track. The retarder is a hydraulic unit including a housing, a cylinder slidably mounted in the housing, a piston rod fixed to the housing, a piston assembly fixed to the piston rod and dividing the cylinder into upper and lower chambers, and a valve arrangement responsive to the flow of hydraulic fluid flowing between the upper and lower chambers. The testing device is constructed and arranged to allow a user to check the resistive force of a retarder installed upon the railway track while standing in an upright position.