To provide a boot that can be easily put on and taken off even by a person having foot deformation due to illness and injuries or the like, that makes walking with sprightly step possible, and that also brings a superior design.

The boot has a gusset that varies the size of an opening and with a plurality of adjusting straps. In the boot, a gusset is provided from the top opening to the vamp, that the adjusting strap can make the opening and the ankle part tightened across the gusset, and that preferably, since a hook function member is designed to be freely adjustable, the adjusting strap can be engaged with the hook function member on the boot body at a desirable position and tightened with a desirable strength.