According to one embodiment, the silicon substrate includes a thinned portion and a side wall provided around the thinned portion. The thinned portion is thinned selectively from one surface. The optical element is formed on a surface of the thinned portion. The surface of the thinned portion is opposite to the one surface of the silicon substrate. The light guide member includes a lens portion, a light guide portion, and an alignment portion. The light guide portion is provided between the lens portion and the optical element. The alignment portion is for an optical connector. The thinned portion of the silicon substrate is provided between the light guide portion of the light guide member and the optical element.