To provide an outside insulation method in which an RC concrete building can be constructed even when a clearance with an adjacent house is small.

A channel-shaped metal fixture 5 and a substantially Z-shaped metal fixture are bonded to both ends of a sheathing board with a heat insulation structure formed by bonding Styrofoam to a temporary frame to be arranged outside a building in a sandwiched state with veneer boards, an outer wall stone material 2 is stuck on building outside bent surfaces of the channel-shaped metal fixture 5 and substantially Z-shaped metal fixture, and a plurality of outside insulation temporary frames which are thus constituted are arranged in a lateral direction. The channel-shaped metal fixture 5 and substantially Z-shaped metal fixture are engaged with each other, and a separator is inserted into a separator fitting hole bored inside bent parts of the engaged channel-shaped metal fixture 5 and substantially Z-shaped metal fixture, and fixed with a nut. An interior-side temporary frame 54 constitutes a temporary frame 54 with a sheathing board 57 and a joist 58, the outside insulation temporary frame and interior-side temporary frame 54 are fixed with the separator, P concrete, and Form Tie (R) 55, and ready mixed concrete is cast in the temporary frame which is thus constructed to structure an outside wall skeleton.