A lamp unit mounting structure includes a mounting panel having a mounting portion, a lamp unit, an elastic fixing member and a restricting member. The elastic fixing member is provided on the lamp unit, and includes a first portion which is extended from the lamp unit, a second portion which has a substantially U-shape, and has a first end being integrally connected to the first portion, a third portion which is extended from a second end of the second portion toward the lamp unit. The engagement portion engages the mounting portion of the mounting panel. The restricting member is provided on the lamp unit, and restricts a movement of the elastic fixing member in a mounting and dismounting direction of the engagement portion relative to the mounting panel. The restricting member has an escape portion which allows a movement of the elastic fixing member toward the lamp unit.