An optical module comprising a mirror unit and a beam splitter unit; the mirror unit comprising: an optical device comprising: a base that includes a main surface (21a, 21b); a movable unit that is supported in the base to be movable along a predetermined direction that intersects the main surface (21a, 21b); an actuator unit for moving the movable unit along the predetermined direction; and an optical function unit that is disposed on the movable unit, wherein the base and the movable unit are constituted by a semiconductor substrate that includes a first semiconductor layer, an insulating layer, and a second semiconductor layer in this order from one side in the predetermined direction, the base is constituted by the first semiconductor layer, the insulating layer, and the second semiconductor layer, the movable unit includes an arrangement portion that is constituted by the second semiconductor layer, the optical function unit is disposed on a surface of the arrangement portion on the one side, the first semiconductor layer that constitutes the base is thicker than the second semiconductor layer that constitutes the base, and a surface of the base on the one side is located over the optical function unit in the predetermined direction; the mirror unit further comprising: an optical function member that is disposed on the other side in the predetermined direction with respect to the optical device, the optical function member being transparent and having a plate shape; and a fixed mirror that is disposed on the other side, which is the side opposite to the optical device, in the Z-axis direction, with respect to the optical function member; wherein the optical function unit is a mirror surface that constitutes a movable mirror in combination with the movable unit; and wherein the beam splitter unit constitutes an interference optical system in combination with the movable mirror and the fixed mirror. a base that includes a main surface (21a, 21b); a movable unit that is supported in the base to be movable along a predetermined direction that intersects the main surface (21a, 21b); an actuator unit for moving the movable unit along the predetermined direction; and an optical function unit that is disposed on the movable unit, wherein the base and the movable unit are constituted by a semiconductor substrate that includes a first semiconductor layer, an insulating layer, and a second semiconductor layer in this order from one side in the predetermined direction, the base is constituted by the first semiconductor layer, the insulating layer, and the second semiconductor layer, the movable unit includes an arrangement portion that is constituted by the second semiconductor layer, the optical function unit is disposed on a surface of the arrangement portion on the one side, the first semiconductor layer that constitutes the base is thicker than the second semiconductor layer that constitutes the base, and a surface of the base on the one side is located over the optical function unit in the predetermined direction; the mirror unit further comprising: an optical function member that is disposed on the other side in the predetermined direction with respect to the optical device, the optical function member being transparent and having a plate shape; and a fixed mirror that is disposed on the other side, which is the side opposite to the optical device, in the Z-axis direction, with respect to the optical function member; wherein the optical function unit is a mirror surface that constitutes a movable mirror in combination with the movable unit; and wherein the beam splitter unit constitutes an interference optical system in combination with the movable mirror and the fixed mirror. an optical function member that is disposed on the other side in the predetermined direction with respect to the optical device, the optical function member being transparent and having a plate shape; and a fixed mirror that is disposed on the other side, which is the side opposite to the optical device, in the Z-axis direction, with respect to the optical function member; wherein the optical function unit is a mirror surface that constitutes a movable mirror in combination with the movable unit; and wherein the beam splitter unit constitutes an interference optical system in combination with the movable mirror and the fixed mirror.