To provide a terminal support device installing structure capable of preventing a terminal support device from slipping out of a bracket, by preventing damage of an arm part.

This terminal support device installing structure includes the terminal support device 10 and the bracket 2. The bracket 2 has an opening part 21, an installing hole part 22, a thick part 23 and an engaging part 4. The thick part 23 is positioned around the opening part 21 and the installing hole part 22. The engaging part 4 is extended in the axial direction X from the thick part 23. The terminal support device 10 has a socket 1, and the socket 1 has an installing object part 17 having an introducing part 16 and a sliding contact part 15, a pair of flange parts 7, a flexible part 9 having a claw part 3 and an arm part 5, and a rotation regulating part 6. The claw part 3 is engaged with the engaging part 4 during rotation. The arm part 5 engageably supports the claw part 3 by the engaging part 4. The rotation regulating part 6 regulates the rotation of the socket 1 after the claw part 3 gets over the engaging part 4 by rotation. The arm part 5 and the claw part 3 exist in a position separated in the axial direction X from the thick part 23 during rotation.