To install an elevator for a chip easily and in a short period.

This method includes a process of carrying a tentative assembly cage 20 into an elevator trunk 1 and installing a cage chain block 21 suspending the tentative assembly cage 20 from a ceiling part 1a of the elevator trunk 1 and a rail chain block 22 suspending a rail, a process of getting on the assembly cage 20 and doing mounting work of metal fittings such as brackets, wiring work and connection work in the elevator trunk 1, a process of mounting rails on brackets from the assembly cage 20, a process of replacing the assembly cage 20 with a regular elevator cage for a ship, a process of installing up and down wire of the regular elevator cage for a ship, and a process to removing each chain block 21, 22.