1. An operation state monitoring apparatus comprising: a counter device for counting a duration of at least one of the ON state or the OFF state of input signals which are independent for each of the operation states of a controlled object; a memory device for memorizing a duration from the operation initiating reference time when the input signal is switched from the ON state to the OFF state or from the OFF state to the ON state; a reference operation state data memory for previously setting the reference operation state of said controlled object; means for generating a signal signifying agreement or disagreement of the actual operation state data given by the data of said counter device and said memory device with the reference operation state data given from said reference operation state memory; and means for setting desirable data selected from the actual operation state data in said reference operation state data memory as the reference operation state data.