The invention provides an optical touch device, including a main body, a keyboard and a light emitting member. The keyboard, placed on the main body and having a first end portion and a second end portion, includes a supporting frame, a keycap and a stopping member. The keycap is connected to the supporting frame and moves between a first position and a second position. The stopping member is connected to the keycap and moves simultaneously with the keycap. The light emitting member generates a light beam to the keyboard. When the keycap is in the first position, the light beam passes through the first end portion to the second end portion, and when the keycap is in the second position, the light beam is terminated by the stopping member, such that the light does not reach the second end portion.