An optical switch includes 2-input 2-output optical switches connected in a multistage, an optical gate provided at each of N-th optical output ports, a driving circuit for operating the 2-input 2-output optical switch, and a driving circuit for operating the optical gate. The driving circuits for operating the 2-input 2-output optical switches are integrated in the vicinity of a control electrode on a waveguide of the 2-input 2-output optical switch. The driving circuits for operating the optical gates are integrated in the vicinity of a control electrode on a waveguide of the optical gates. The waveguide of the 2-input 2-output optical switch and the waveguide of the optical gate each has a p layer, an i layer, and an n layer sequentially formed on a semi-insulating substrate. The optical switch has a trench reaching the semi-insulating substrate between the 2-input 2-output optical switch and the optical gate.