Abstract: A muscle relaxation monitoring device monitors the state of muscle relaxation without placing an excessive burden on the patient. The muscle relaxation monitoring device has a current stimulator to supply a stimulating current to muscles of a patient, a reaction detector to detect a stimulus response of the muscle stimulated by the current stimulator. The stimulating current supplied to the muscles of the patient before the application of the muscle relaxant and the stimulating response corresponding to the stimulating current value are recorded in a memory, and when the stimulating response is saturated, the stimulating current value immediately before saturation is used as the optimum current value to be supplied to the patient after administration of the muscle relaxant.