To provide a concrete form assembly structure capable of facilitating dismantling work after concrete is placed and having high effect for preventing water leak and provide a separator for the form enabling permanent and stable use and capable of contributing to shortening of construction term.

This separator for the form is composed of a separate bolt 16 having male screw parts 14a, 14b at both ends of a steel bar 12 and a pair of separator holding cones 18a, 18b screw-fitted in the male screw parts 14a, 14b of the separate bolt 16, respectively. Each separator holding cone 18a, 18b is constituted in such a way that a nut 22 with a pivot foot bolt is buried into a cement-made cone main body 20, a blind nut hole 30 in which the male screw parts 14a, 14b of the separate bolt 16 are screw-fitted is formed in the nut 22 with the pivot foot bolt, and a constriction part 36 capable of removing breakage is formed in a basic part of a bolt shaft part 28 extended on an axis from a nut part 26.