To provide a terminal block having a structure for facilitating the mounting operation of a coil spring to the terminal block, and a method for assembling the terminal block. A spring supporting part (25a) has a supporting surface (251a) in which one end of a coil spring (5a) contacts, and a spring end holding portion (252a) for preventing the end of the coil spring contacting supporting surface (251a) from displacing in the radial direction of the coil spring. Spring end holding portion (252a) extends form supporting surface (251a) and is arranged at a part of the periphery of supporting surface (251a), such that spring end holding portion (252a) does not block a slit (27a). The width of slit (27a) is smaller than an outer diameter of coil spring (5a), and the length of slit (27a) is preferably equal to or larger than the radius of coil spring (5a).