To provide a protection method for building parts not requiring the supercargo work for the building parts at the time of covering the parts with a protective cover and not requiring substantially labor of folding either.

In a protection method for building units 1 in which the building units 1 (building parts) mounted on and carried on a transport car 2 are covered with a protective cover 3, the protective cover 3 is formed of a flexible sheet material, and the protective cover 3 is mounted on the transport car 2 in the state of being rolled into the roll material shape by using a take-up device 4, and the building units 1 are protected by stretching the protective cover 3 at the time of covering the building units.