To provide a method for forming a game board by which its machining accuracy can be prevented from degrading by enhancing the sucking effect of the game board in a game board fixing process.

The method for forming a game board is characterized by performing; a mounting process of mounting a game board 30 on a vacuum table 110 where an elastically deformable sealing member 70 is provided on a mounting surface 110aa and a vacuum hole is formed so as to form a space 90 by a sealing part 70 with a sub table 115, the game board fixing process of sucking the air of the space between the sub table 115 and the game board 30 formed by the sealing member 70 by the vacuum hole, sealing the part between the sub table 115 and the game board 30 by the sealing member 70 and sucking and fixing the game board 30 to the sub table 115; and a machining process of machining the game board sucked and fixed to the sub table 115 by the game board fixing process.