To provide a side turn signal lamp that is attached to a fender panel without any backlash and gap and can secure a high-quality feel.

A plurality of contacting parts 2a and 2b are formed on an attaching surface 2A of a lamp housing 2 of the side turn signal lamp 1 to each of the fender panels 11' attached to each of the fender panels 11' by being inserted into and engaged with attaching holes 11a' formed in the fender panels 11' on the right and left of a vehicle, so that the selected contact part 2a contacts an outer surface of each of the fender panels 11', thereby keeping each side turn signal lamp 1 attached to each of the fender panels 11' so as to have a smaller gap on the top between the lamp housing 2 and each of the fender panels 11' than the gap on the bottom.