To provide a design method of an outer shell PCa column designable in a desired quality, by setting shearing strength, flexural strength and sticking strength of the outer shell PCa column to design accuracy equal to an integrally driving RC column, without forming the outer shell PCa column into an excessive quality, in the outer shell PCa column composed of an outer shell PCa member using a high strength member and a post-placing concrte part different in concrete strength from the outer shell PCa member.

This column design method uses a specific shearing strength method to a PC column; and makes a shearing design by determining a concrete strength effectiveness factor ν0 by a specific expression with concrete strength σB and horizontal reinforcing bar yield strength σwy as equivalent concrete strength eσB and reinforcing bar effective yield strength eσwy respectively determined by the specific expression. The design method uses an NZ stress block method, and makes a bending design by using the equivalent concrete strength eσB as concrete strength.