A fixing device for a panel comprising: a rectangular metal plate with opposed two sides (1a, 1b), an intermediate line being defined parallel to the two sides (1a, 1b) between the two sides (1a, 1b), a main body portion being formed by an area from the intermediate line to one side of the two sides (1a, 1b), a slit being formed at an area from the intermediate line to the other side among the two sides (1a, 1b), a plurality of leaf spring-shaped strip plates (41, 42 and 43) being formed continuous with the main body portion at the intermediate line; and a nail hole disposed at the main body portion for fixing to a wall body, wherein the plurality of leaf spring-shaped strip plates (41, 42 and 43) are formed orthogonal to the two sides (1a, 1b) and then bent at the intermediate line toward a same direction with respect to the main body portion, at least one of the plurality of the strip plates (41, 42 and 43) is bent to a predetermined direction at a bend position parallel to and away from the intermediate line at a predetermined distance, remaining strip plates (42, 43) are bent to a direction opposite from the predetermined direction at a bend position parallel to and away from the intermediate line at a predetermined distance, an area from the intermediate line of each strip plate (41, 42 and 43) to the bend position is fixing piece (41a, 42a and 43a), an area from the bend position to a distal end is lock piece (41b, 42b, and 43b) characterized in that with respect to the main body portion an inclined angle (θ1) of the fixing piece disposed at the at least one strip plate of the plurality of strip plates (41,42,43), on which the lock piece is bent to the predetermined direction is formed to have a different angle from an inclined angle (θ2) of the fixing pieces (42a, 43a) disposed at said remaining strip plates (42 and 43) with respect to the main body portion, and when a panel is expanded, each of the fixing pieces (41a, 42a and 43a) is elastically deformed to the extent that the inclined angle (θ1) of the fixing piece disposed at the at least one strip plate of the plurality of strip plates (41, 42, 43), on which the lock piece is bent to the predetermined direction and the inclined angle of the fixing pieces (42a and 43a) disposed at said remaining strip plates (42 and 43) become the same angle. a rectangular metal plate with opposed two sides (1a, 1b), an intermediate line being defined parallel to the two sides (1a, 1b) between the two sides (1a, 1b), a main body portion being formed by an area from the intermediate line to one side of the two sides (1a, 1b), a slit being formed at an area from the intermediate line to the other side among the two sides (1a, 1b), a plurality of leaf spring-shaped strip plates (41, 42 and 43) being formed continuous with the main body portion at the intermediate line; and a nail hole disposed at the main body portion for fixing to a wall body, wherein the plurality of leaf spring-shaped strip plates (41, 42 and 43) are formed orthogonal to the two sides (1a, 1b) and then bent at the intermediate line toward a same direction with respect to the main body portion, at least one of the plurality of the strip plates (41, 42 and 43) is bent to a predetermined direction at a bend position parallel to and away from the intermediate line at a predetermined distance, remaining strip plates (42, 43) are bent to a direction opposite from the predetermined direction at a bend position parallel to and away from the intermediate line at a predetermined distance, an area from the intermediate line of each strip plate (41, 42 and 43) to the bend position is fixing piece (41a, 42a and 43a), an area from the bend position to a distal end is lock piece (41b, 42b, and 43b) characterized in that with respect to the main body portion an inclined angle (θ1) of the fixing piece disposed at the at least one strip plate of the plurality of strip plates (41,42,43), on which the lock piece is bent to the predetermined