A busbar holding structure holds at least one of plural busbars to a wires routing body. The plural busbars electrically connect plural cell batteries constituting a battery assembly. The busbar holding structure includes a bottom wall, a partition wall erected from a portion of a peripheral edge of the bottom wall, a lock portion provided on the partition wall and configured to lock a side end portion of the busbar on the wires routing body, and a first projection that projects perpendicularly from the bottom wall and is to be fitted in a through-hole provided in the busbar. A fitting gap between the first projection and the through-hole is set so as to restrict an inclination angle of the busbar with respect to the first projection and to thereby prevent the busbar from being unlocked from the lock portion.