provided is a mounting member having a light receiving element , capable of constraining increase in size and of arranging a plurality of laser element portions closer to each other . the mounting member includes three or more electrodes , which respectively include element mounting portions arranged in a first direction , and a light receiving element disposed in a second direction intersecting with the first direction relative to the element mounting portions . the length in the second direction of at least one of the element mounting portions disposed at both ends in the first direction among the three or more element mounting portions is smaller than the length in the second direction of an element mounting portion disposed at an inner position in the first direction among the three or more element mounting portions .