An operation control apparatus is provided of a compressor having a rotary shaft which is rotated by a driving apparatus by way of a clutch. The operation control apparatus comprises a recess or projection formed in or on one end surface of the rotary shaft as a portion-to-be-sensed offset from the axis thereof, an electromagnetic sensor disposed in facing relation with a locus described by the recess or projection according to the rotation of the rotary shaft, and a pulse monitoring circuit connected to the sensor. The sensor generates a periodic pulse signal in response to rotation of the rotary shaft. The pulse monitoring circuit generates a clutch release commanding signal to the clutch when it receives no pulse signal from the sensor for a predetermined time duration to protect the driving apparatus.