A loom with a fixing device for a support body, the loom including a sley having a front surface, a rear surface, and a T-shaped groove, the T-shaped groove having a front surface opening portion that is opened at the front surface and a groove that is located closer to the rear surface than the front surface opening portion is, the fixing device comprising: a fastening member having a T-shaped head portion to be inserted into the T-shaped groove and placed in the groove, a shank portion extending from the T-shaped head portion, and a threaded portion formed on a tip end of the shank portion; and the support body configured to support an object to be supported, and having a facing surface facing the front surface on one side of the support body in a thickness direction of the support body and a through hole extending through the support body in the thickness direction, wherein the T-shaped head portion is placed in an engagement state in which the T-shaped head portion is engaged with an upper wall and a lower wall of the groove when the fastening member is rotated by a predetermined angle in an engagement direction in a state where the T-shaped head portion is inserted through the front surface opening portion into the groove, the facing surface faces the front surface of the sley, and the threaded portion is inserted through the through hole of the support body, wherein the threaded portion is tightened with a nut to cause the sley to be held between the support body and the T-shaped head portion so that the support body is fixed to the sley, wherein the fastening member includes a protrusion protruding from the shank portion in a radial direction of the shank portion, and wherein the support body includes a restriction surface configured to restrict rotation of the T-shaped head portion in a direction opposite to the engagement direction with the restriction surface engaged with the protrusion in the engagement state, characterized in that the support body includes a guide surface connecting the facing surface to the restriction surface, and the guide surface is configured to guide the protrusion so that the T-shaped head portion rotates in the engagement direction when the threaded portion is tightened with the nut. a fastening member having a T-shaped head portion to be inserted into the T-shaped groove and placed in the groove, a shank portion extending from the T-shaped head portion, and a threaded portion formed on a tip end of the shank portion; and the support body configured to support an object to be supported, and having a facing surface facing the front surface on one side of the support body in a thickness direction of the support body and a through hole extending through the support body in the thickness direction, wherein the T-shaped head portion is placed in an engagement state in which the T-shaped head portion is engaged with an upper wall and a lower wall of the groove when the fastening member is rotated by a predetermined angle in an engagement direction in a state where the T-shaped head portion is inserted through the front surface opening portion into the groove, the facing surface faces the front surface of the sley, and the threaded portion is inserted through the through hole of the support body, wherein the threaded portion is tightened with a nut to cause the sley to be held between the support body and the T-shaped head portion so that the support body is fixed to the sley, wherein the fastening member includes a protrusion protruding from the shank portion in a radial direction of the shank portion, and wherein the support body includes a restriction surface configured to restrict rotation of the T-shaped head portion in a direction opposite to the engagement direction with the restriction surface engaged with the protrusion in the engagement state, characterized in that the support body includes a guide surface connecting the facing surface to the restriction surface, and the guide surface is configured to guide the protrusion so that the T-shaped head portion rotates in the engagement direction when the threaded portion is tightened with the nut.