An image forming apparatus which is capable of obtaining stable and satisfactory cleaning performance and fixing performance without holding, in an image forming unit which forms an image on a recording material based on a video signal, data for performing maintenance of the image forming unit. An instruction for periodically alternately setting H and L in the port output signal setting register is written in test ROM. The electrocardiograph stores a cardiogram produced when the instruction signal is received from the communication device as a reference cardiogram corresponding to the selected posture discriminating it from other cardiograms.