A transmitter that is difficult to be affected by structural constraints includes: a liquid crystal board; a first board having translucency; and a second board; and a control unit that changes, by switching transmittance of the liquid crystal board with respect to outside light through application, to the liquid crystal board, of a control voltage corresponding to a signal to be transmitted, an amount of light reflected by the first board and emitted toward the receiver via the liquid crystal board, wherein the control unit maintains, when switching the transmittance of the liquid crystal board to a low transmittance, the transmittance of the liquid crystal board at the low transmittance until the outside light that passed through the liquid crystal board is reflected by the second board and reaches the liquid crystal board.