A fixing device for a panel which can absorb a dimensional change due to expansion of the siding board is provided. A comb-shaped slit is formed at an area from the intermediate line C defined between opposed two sides of a rectangular metal plate to form leaf spring-shaped strip plates 41, 42 and 43. The strip plates are bent at the intermediate line C and a bend line F to form fixing pieces 41a, 42a and 43a and lock pieces 41b, 42b, and 43b so as to lock fixing ends 51a and 52b of the siding board 50. Moreover, an inclined angle θ1 of the fixing piece 41a disposed at the strip plate 41 is formed to have a different angle from an inclined angle θ2 of the fixing pieces 42a, 43a disposed at the remaining strip plates 42 and 43. Thereby the strip plates can be elastically deformed.