To provide a form assembling method suitable for form using metallic form plates, and to provide a crosspiece fixing member suitable for use in the method.

A plurality of separators 2 are penetrated through the form plate 1 at suitable intervals, and a long crosspiece 3 formed of a pair of plate portions 3a and 3b intersecting each other like a hook in cross section, is arranged along a row of the separators 2 such that one of the plate portion 3a makes contact with an external surface of the form plate 1. Then, the plate portion 3a of the crosspiece 3, making contact with the form plate 3a is fixed to the form plate so as not to move in a direction that intersects the form plate, by using a first crosspiece fixing member 4 attached to a portion of the separator 2, which protrudes from the form plate, and the plate portion 3b intersecting the form plate is fixed to the form plate so as not to move in a direction in parallel with the form plate, by using a second crosspiece fixing member 5 fixed to a portion of the separator 2 other than the separator to which the first crosspiece fixing member is attached.