A fiber structure body being a multi-layered fabric, the multi-layered fabric including: a plurality of first yarn layers each including a plurality of first yarns; and a plurality of second yarn layers each including a plurality of second yarns that intersects with the first yarns, the first yarn layers and the second yarn layers being stacked on top of each other and bound by a plurality of binder yarns in a stacking direction in which the first yarn layers and the second yarn layers are stacked, the fiber structure body comprising: a main body in which all of yarn layers of the first yarn layers and the second yarn layers of the multi-layered fabric are bound by the binder yarns; a branch portion continuous with the main body at least at one end of the main body in a yarn main-axis direction of the first yarns, the branch portion including a first formation and a second formation that are branched out from the yarn layers of the multi-layered fabric, the first formation being disposed at one end of the multi-layered fabric in the stacking direction and the second formation being disposed at the other end of the multi-layered fabric in the stacking direction; an inner periphery curved in a plan view; and an outer periphery curved in the plan view outside the inner periphery wherein the yarn main-axis direction of the first yarns extends in a circumferential direction and a yarn main-axis direction of the second yarns extends in a radia direction, where the radial direction refers to a direction in which a shortest line connecting the inner periphery and the outer periphery of the fiber structure body extends and the circumferential direction refers to a direction in which the inner periphery and the outer periphery of the fiber structure body extend, and a main axis of each of closest second yarns closest to a branching boundary line among the second yarns of the main body is parallel to the branching boundary line in the branch portion, the branching boundary line extending along a location from which the first formation and the second formation of the branch portion start branching out. a plurality of first yarn layers each including a plurality of first yarns; and a plurality of second yarn layers each including a plurality of second yarns that intersects with the first yarns, the first yarn layers and the second yarn layers being stacked on top of each other and bound by a plurality of binder yarns in a stacking direction in which the first yarn layers and the second yarn layers are stacked, the fiber structure body comprising: a main body in which all of yarn layers of the first yarn layers and the second yarn layers of the multi-layered fabric are bound by the binder yarns; a branch portion continuous with the main body at least at one end of the main body in a yarn main-axis direction of the first yarns, the branch portion including a first formation and a second formation that are branched out from the yarn layers of the multi-layered fabric, the first formation being disposed at one end of the multi-layered fabric in the stacking direction and the second formation being disposed at the other end of the multi-layered fabric in the stacking direction; an inner periphery curved in a plan view; and an outer periphery curved in the plan view outside the inner periphery a main body in which all of yarn layers of the first yarn layers and the second yarn layers of the multi-layered fabric are bound by the binder yarns; a branch portion continuous with the main body at least at one end of the main body in a yarn main-axis direction of the first yarns, the branch portion including a first formation and a second formation that are branched out from the yarn layers of the multi-layered fabric, the first formation being disposed at one end of the multi-layered fabric in the stacking direction and the second formation being disposed at the other end of the multi-layered fabric in the stacking direction; an inner periphery curved in a plan view; and an outer periphery curved in the plan view outside the inner periphery the yarn main-axis direction of the first yarns extends in a circumferential direction and a yarn main-axis direction of the second yarns extends in a radia direction, where the radial direction refers to a direction in which a shortest line connecting the inner periphery and the outer periphery of the fiber structure body extends and the circumferential direction refers to a direction in which the inner periphery and the outer periphery of the fiber structure body extend, and a main axis of each of closest second yarns closest to a branching boundary line among the second yarns of the main body is parallel to the branching boundary line in the branch portion, the branching boundary line extending along a location from which the first formation and the second formation of the branch portion start branching out.