To add a new interesting property to a game.

When BB is determined in a winning combination determination section 40, a player selects to shift to an NBB mode or perform conversion lot drawing to determine a shift to an SBB mode. When the player selects to shift to the NBB mode, the player makes BB win. When the player selects to carry out lot drawing for conversion to the SBB mode, the player operates a stop button to prevent the BB from winning until a game in which the player successfully gets a cherry. In a game where the player gets a cherry, when the player wins the cherry and the BB simultaneously, a simultaneous winning detection signal generation section 42 inputs a simultaneous winning detection signal to a winning combination conversion lot drawing section 43. The winning combination conversion lot drawing section 43 carries out lot drawing for conversion to the SBB mode. When the player determines to shift to the SBB mode, a control section 30a reads an execution program for the SBB mode from the ROM area of a memory 31 and implements a shift to the SBB mode.