PURPOSE: A switching signal generator is provided to be safe with using a photodiode and a phototransistor maintaining an electrically insulated state inside a changeover regulator and to save cost as compared to a magnetic switch. CONSTITUTION: A switching signal generator in a gas container changeover regulator is composed of a shut-off cover(30) inhibiting the light from outside; a reflective/absorbing face(31) closed by the shut-off cover; a partition(32) for dividing the space closed by the shut-off cover; a photodiode(33) irradiating the light from a reflective face; a phototransistor(34) generating a changeover signal by detecting the light reflected from the photodiode. The reflective/absorbing face is switched to a reflective face when gas is exhausted in a used gas container and is switched to an absorbing face when a gas supplying pipe is connected to the gas container filled with gas afterward.
