To provide a fitting unit for fixing a running rail capable of preventing generation of metal fatigue and fatigue failure (breakage of bolt) in a foundation bolt for fixing a running rail.

This fitting unit is formed by a pressing piece 4 having a rail locking blade part 4a, a cylindrical bolt collar 6 inserted in a hole of the pressing piece 4, an eccentric collar 8 fitted in a counter bore part 4c of the top face of the rail pressing piece 4, and at least one spring 9 wound round the outer surface of the bolt collar 6 projected on the top part of the pressing piece 4, and the rail is laterally centered by the eccentric collar 8 and fixed by the pressing piece 4.