A plurality of recesses (15) is formed in a surface of first block (10), the surface facing second block (20). The plurality of recesses (15) are formed in a region different from a region in which laser element (40) is disposed when viewed from a direction in which first block (10) and second block (20) are stacked. Each of recesses (15) is provided with a spacer member (50) having insulation properties. Spacer member (50) partly protrudes from corresponding recess (15). Spacer member (50) is sandwiched between first block (10) and second block (20).