Disclosed is monitoring device of monitoring a state of a substrate processing process in a substrate processing apparatus. The monitoring device includes: an imaging unit configured to image a processing state of the substrate processing process; a storage unit; a storage control unit configured to store a moving picture imaged by the imaging unit after adding a time stamp to the moving picture; a group classification unit configured to group a plurality of moving pictures stored in the storage unit into moving pictures of a normal group and moving pictures of a group other than the normal group; and a threshold generation unit configured to generate a threshold for detecting an abnormal moving picture based on the moving pictures of the normal group grouped by the group classification unit.