The device automatically alarms the usefulness of toilet device relates to display, in particular of toilet lock is provided to an exterior state controller space star display unit rotates in the opposite direction for globally toilet is in use is light to so confirmation user from outside without TIR hologram and transmits it to the main body display usefulness of a toilet relates to device. To this end the device, real estate of toilet door is provided to toilet door or internal state controller the non-displaying the Image on the display section on/off power and switch for a power supply the; toilet is side door, said power supply accuracy of measuring the residual capacity of each toilet according to on/off in space star in-use user that are individually of a channel number and a display section, a pattern specifying an internal state controller; is mounted on the doorway toilet, according to accuracy of measuring the residual capacity of power supply said transmitting toilet on/off in space star in-use user usefulness of external use represented by overall parts by display curd together characterized by provides indoor usefulness of display device.