To facilitate the installation of a net without excavating an underground part by connecting an outer frame formed of shape steel and slide guides of a game ball court to be a structure with weight, raising and supporting poles at the structure, and expanding the net in such a way as to be freely attached and removed.

An outer frame of a ball game court is formed into a cross- sectionally rectangular shape through the use of unequal sided angle steel, and slide guides 2 are connected to the outside of the outer frame to obtain a structure with weight. Pole guides 3 are fixed to the slide guides 2 on both right and left sides, and rectangular steel tube poles 4 and slide poles 5 are assembled to the pole guides 3 through the use of bolts 6 and 8, etc. In addition, by towing wires wound on pulleys 6 for a net at the tips of the rectangular steel tube poles 4 with a winch or a jack, the net is pulled up, expanded, and supported. By this constitution, it is possible to install and disassemble the net easily and to prevent its overturning reliably at the time of installing the net.