To provide a stance supporting mechanism effective as a boot binding mechanism itself regardless of an accessory and attachable even to any boots of a step-in type in the stance supporting mechanism as the accessory provided with a structure for which the heel part of the boot is simplified.

This stance supporting mechanism is mainly constituted of a link 4, a bearing attachment part 2 for supporting a bearing 1 provided with a bearing surface constituted attachably to the heel part of a snowboard boot and a shaft holding member constituted attachably to the leg part of the snowboard boot. The link 4 is formed as a swing end 5 whose one end is supported by the bearing surface and is swingable to a boot inner side from an almost upright state and swing to a boot outer side is restricted. The other end of the link 4 is a lever end 6 engageable with the link holding member 3.