To facilitate installation by eliminating a projection on a top plate part in contact with a boot bottom and by miniaturizing the size in a step-in type binding device for catching the projections in the both sides of the bottom of the snowboard boot.

This step-in type binding device for the snowboard is so formed that a rotary shaft for left/right catching arms is separated from a left/right connecting shaft carrying one-directional rotation brake device, and a pair of rotation transmitting devices is provided between the both so as to accelerate the left/right connecting shaft relative to the rotation of the catching arms. Thereby, the rotation force acting on the one-directional rotation brake device can be reduced, the brake device can be miniaturized, and the freedom degree in arranging the left/right connecting shaft can be obtained.