Abstract: Provided is a machine state detecting device capable of easily detecting the state of a machine, regardless of whether an unknown operation that is not expected to cause damage is performed. A state detecting device 100 includes a collection device 1a that collects, at a plurality of times, state information if indicating the state of the machine that changes chronologically, and an arithmetic processing device 1b that processes a plurality of pieces of the state information if collected at the plurality of times to detect the state of the machine.