To simply and freely assemble and repeatingly use forms having different sizes, to reduce labor in installation and transportation work and allow recycling for cost reduction and resource saving.

A form consists of a plurality of synthetic resin channels 2 and bolts 4 for connecting the channels 2 together. The webs 22 of the plurality of channels 2 are arranged to be flat with one another and the adjacent flanges 21 are connected together with bolts 4 to form face materials 3. The flange 21 of the channels 2 at the end of one face material 3 of the plurality of face materials 3 is connected to the web 22 of the channels 2 at the end of the other face material 3 with the bolts 4.