A shoe comprising: a flexible shell (10A-10R, 10A1-10A2, 10B', 10C', 10H', 10H1, 10H2, 10K') having an internal space receiving a foot of a wearer; and a sole body accommodated in the shell (10A-10R, 10A1-10A2, 10B', 10C', 10H', 10H1, 10H2, 10K') and supporting a sole of the foot of the wearer, wherein the shell (10A-10R, 10A1-10A2, 10B', 10C', 10H', 10H1, 10H2, 10K') includes a bottom wall portion and a peripheral wall portion erected from a peripheral edge of the bottom wall portion, the bottom wall portion and a portion of the peripheral wall portion adjacent to the bottom wall portion define a lower space of the internal space in which the sole body is disposed, and a portion of the peripheral wall portion located above the portion adjacent to the bottom wall portion defines at least a portion of an upper space of the internal space in which the wearer's foot is inserted, the bottom wall portion covers a lower surface of the sole body and thus has an external surface configuring a tread of the shoe, the shoe further comprises an upper body accommodated in the shell (10A-10R, 10A1-10A2, 10B', 10C', 10H', 10H1, 10H2, 10K') and at least covering an instep of the foot of the wearer, the upper body is in a form of a bag having an opening at a portion thereof corresponding to a topline through which the foot of the wearer is inserted, the upper body is disposed along an inner surface of the portion of the shell (10A-10R, 10A1-10A2, 10B', 10C', 10H', 10H1, 10H2, 10K') that defines the upper space and along an upper surface of the sole body, and the sole body is thus sandwiched between the bottom wall portion and the upper body, the upper body is formed of heat-shrinkable synthetic fibre, and the shell (10A-10R, 10A1-10A2, 10B', 10C', 10H', 10H1, 10H2, 10K') includes in the peripheral wall portion a portion covering the instep of the foot of the wearer and being composed of resin or rubber and composed of a harder material than a woven material, a knitted material, and/or a nonwoven fabric, and wherein the shell (10A-10R, 10A1-10A2, 10B', 10C', 10H', 10H1, 10H2, 10K') is configured such that at least the peripheral wall portion including the portion covering the instep and the bottom wall portion including a portion defining the tread are integrally composed of a single member. a flexible shell (10A-10R, 10A1-10A2, 10B', 10C', 10H', 10H1, 10H2, 10K') having an internal space receiving a foot of a wearer; and a sole body accommodated in the shell (10A-10R, 10A1-10A2, 10B', 10C', 10H', 10H1, 10H2, 10K') and supporting a sole of the foot of the wearer, wherein the shell (10A-10R, 10A1-10A2, 10B', 10C', 10H', 10H1, 10H2, 10K') includes a bottom wall portion and a peripheral wall portion erected from a peripheral edge of the bottom wall portion, the bottom wall portion and a portion of the peripheral wall portion adjacent to the bottom wall portion define a lower space of the internal space in which the sole body is disposed, and a portion of the peripheral wall portion located above the portion adjacent to the bottom wall portion defines at least a portion of an upper space of the internal space in which the wearer's foot is inserted, the bottom wall portion covers a lower surface of the sole body and thus has an external surface configuring a tread of the shoe, the shoe further comprises an upper body accommodated in the shell (10A-10R, 10A1-10A2, 10B', 10C', 10H', 10H1, 10H2, 10K') and at least covering an instep of the foot of the wearer, the upper body is in a form of a bag having an opening at a portion thereof corresponding to a topline through which the foot of the wearer is inserted, the upper body is disposed along an inner surface of the portion of the shell (10A-10R, 10A1-10A2, 10B', 10C', 10H', 10H1, 10H2, 10K') that defines the upper space and along an upper surface of the sole body, and the sole body is thus sandwiched between the bottom wall portion and the upper body, the upper body is formed of heat-shrinkable synthetic fibre, and the shell (10A-10R, 10A1-10A2, 10B', 10C', 10H', 10H1, 10H2, 10K') includes in the peripheral wall portion a portion covering the instep of the foot of the wearer and being composed of resin or rubber and composed of a harder material than a woven material, a knitted material, and/or a nonwoven fabric, and wherein the shell (10A-10R, 10A1-10A2, 10B', 10C', 10H', 10H1, 10H2, 10K') is configured such that at least the peripheral wall portion including the portion covering the instep and the bottom wall portion including a portion defining the tread are integrally composed of a single member.