PURPOSE: To facilitate conveyance by lowering bulk at the time of conveyance, and to enable conveyance without damaging a lighting window.

CONSTITUTION: A connecting frame 3 is installed at the opening edge of an opening section 3 formed at the specified place of a roof panel body 1. A lighting window 4 is disposed so as to cover the opening section 2. A frame 5 for the lighting window mounted on the peripheral section of the lighting window 4 and the connecting frame 3 are coupled detachably. A drip hole for draining condensate is formed at the underwater-side end section of the connecting frame 3 arranged on the underwater side. A check valve preventing the back flow of rainwater from an outdoor section may also be set up to the drip hole.