The invention discloses a photoelectric cutting knife cutting depth monitoring mechanism device, and relates to the field of optic-mechanical-electric application devices. A first lifting cross plateis fixedly connected at the end side of a first edge side fixed connecting plate, an infrared transmitting mechanism is mounted on one side of the first lifting cross plate, an infrared receiving mechanism is mounted on one side of a second lifting cross plate, a cutting knife rotating disk is movably mounted on the end side of a second lifting connecting rod mechanism, and a power device for driving the cutting knife rotating disk is arranged on the end side of the second lifting connecting rod mechanism. According to the device, the photoelectric position of the current cutting knife rotating disk is monitored through the infrared transmitting mechanism and the infrared receiving mechanism, the width of a partition area of the current cutting knife rotating disk is monitored through theinfrared transmitting mechanism and the infrared receiving mechanism, current cutting depth is analyzed and calculated, so that cutting depth of the cutting knife rotating disk for a workpiece plate is effectively controlled, the cutting accuracy of the workpiece plate is greatly improved, and the processing quality of a metal plate workpiece can be improved.