To provide a form assembling method enable the simple and accurate forming of a form for a concrete column.

Corner forms 1 are vertically provided corresponding to the corners of angular columns. Form panels 2 are arranged between both adjacent corner frameworks 1. The form panels 2 are connected and fixed to the corner forms 1 to form a rectangularly cylindrical form 3. On the outer periphery of the rectangularly cylindrical form 3 formed by the corner forms 1 and the form panels 2, pairs of shape holder 4 formed from a pair of almost L-shape frame-end big materials 17 are arranged in a vertical direction to constrain the rectangularly cylindrical form.