To provide a fixing method for transportation of building unit capable of stably fixing a building unit having a different length from a standard dimension building unit to a standard dimension building unit transporting means without performing any work to a deck.

A standard dimension building unit transporting means 2 is utilized, and one short side 1a of a building unit 1 having a different length from a standard dimension building unit 70 is fixed to a standard dimension building unit fixing part 6a provided in a deck 5, and each lock tool 91 fitted to an upper end of the other short side 1b and each lock tool 93 fitted to the deck 5 are fixed by fastening by a lock rope 95.