According to one embodiment, an optical transmitter/receiver circuit device includes a transmitter circuit including a transition time adjusting circuit to obtain a second voltage signal from a first voltage signal and a voltage-current converter circuit that converts the second voltage signal to a first current signal, a light-emitting element to convert the first current signal to an optical signal, a light-receiving element to convert the optical signal to a second current signal, and a receiver circuit including a current-voltage converter circuit that converts the second current signal to a third voltage signal, a pulse generation circuit to generate rise and fall pulse from the third voltage signal and a decoder circuit that generates a fourth voltage signal in synchronism with the pulse.