An arrangement and a method for monitoring the operational condition of an automatic door in an elevator, particularly a passenger and/or goods elevator, or in a building, the arrangement includes an automatic door which includes one or more door leaves, which slide horizontally in their location, a door operator, which includes a door motor and a door mechanism for moving the door leaf horizontally in its location, a closing device for closing the automatic door, a control system for the door operator for controlling the door motor, a device configured to define the operational condition of the closing device and the door mechanism of the automatic door, the device configured to define the operational condition of the closing device and the door mechanism of the automatic door includes a mechanism configured to determine the mechanical energy of the shaft in the door motor of the automatic door during an operating cycle.