A transmitter (100) that is difficult to be affected by structural constraints is a transmitter that transmits a signal to a receiver by changing an amount of light emitted, and the transmitter includes: a control unit (101) that generates a control voltage corresponding to a signal to be transmitted; a reflector (102) that reflects sunlight; and a liquid crystal board (103) that receives reflected light that is sunlight reflected by the reflector (102) and changes, according to the control voltage, the amount of light emitted toward the receiver, by allowing the reflected light to pass through the liquid crystal board (103).