A plurality of semiconductor photodetecting elements have a planar shape having a pair of first sides opposed to each other in a first direction and a pair of second sides being shorter than the pair of first sides and opposed to each other in a second direction perpendicular to the first direction, and are disposed on a base so as to be adjacent to each other in juxtaposition. A plurality of bump electrodes each are disposed on sides where the pair of first sides lie in each semiconductor photodetecting element, to electrically and mechanically connect the base to each semiconductor photodetecting element. A plurality of dummy bumps are disposed so that at least one dummy bump is disposed on each of sides where the pair of second sides lie in each semiconductor photodetecting element, to mechanically connect the base to each semiconductor photodetecting element.