A composite optical device 1 includes a first optical section 10 having an optical functional surface 11 and a second optical section 20 bonded to the first optical section 10 on the optical functional surface 11. The optical functional surface 11 includes a smooth part 13 and a concave-convex part 12 adjacent to each other, and is constructed so that a position P2, along a normal direction of the smooth part 13, of a concave bottom of the concave-convex part 12 can be closer to the center of the first optical section 10 than a position P1 along the normal direction of an end of the smooth part 13 on a side of the concave-convex part 12 in a boundary vicinity portion NR between the smooth part 13 and the concave-convex part 12.