To provide a lightweight reinforced panel which has a high pressure- resisting strength and which can be formed from empty cans for food etc., which are yielded in a great quantity, without subjecting them to any particular processing.

An outer casing 3 having an outside shape identical to a conventional side gutter lid is formed from a reinforced synthetic resin, and inside of this outer casing 3 a number of empty cans 5 having a certain size are accommodated in such a way that their direction over the heights is extending across the thickness of the outer casing 3 and their peripheral walls 23 touch directly one another. Accordingly the peripheral walls 23 of all empty cans 5 work like an aggregate, so that the resultant panel is light in the weight, has a high pressure-resisting strength, and can be embodied at a low cost owing to utilization of the waste which is yielded in a great quantity without subjecting it to any particular processing.