Abstract: A clamping apparatus of construction molding board has a base, a base body, a press bar, and a torsion spring. The base is provided with a through hole. The base body of U-shaped construction is made integrally with the base such that the base body extends upwards from the base. The base body contains a receiving space having a rear portion provided with a canal in communication with the through hole of the base. The press bar has a bottom end provided thereon with a serrated arresting portion. The press bar is mounted pivotally in the receiving space by a shaft pin in such a manner that the arresting portion is opposite in location to the canal. The torsion spring is composed of two ring bodies sharing a common end which forms a pressing portion of an inverted U shape. The two ring bodies are provided respectively with another end which forms a supporting portion.