To simplify construction work, shorten a construction term, and reduce cost of construction without using plywood to allow a worker to confirm a concrete placed surface by using a form made of foaming resin on only an external wall side insulating outside heat because, when a heat insulating material made of foaming resin is used for internal and external forms, there are disadvantages that the worker cannot confirm a finish condition after placing concrete and improper construction sections caused by workers' insufficient experience and skill in construction work are hidden.

This concrete form for the external wall is composed of an outer frame 2 constituted by fitting side fringes of an expanded polystyrene board 21 into a plurality of plastic connection devices 22 sequentially and serving also as the outer heat insulating material and an inner frame 3 capable of being dismantled and used repeatedly by linking hollow panels 3a provided with a transparent or semi-transparent window part allowing the worker to see the concrete placed in a plurality of sections vertically through it sequentially.