PURPOSE: To easily secure the gravity-free state by installing a buoyancy adjusting chamber by dividing the inside of a balloon onto which a means for holding a passenger is installed in the lower part and balancing the buoyancy of the balloon to the body weight of the suspended passenger by adjusting the quantity of the gas in the buoyancy adjusting chamber and generating the gravity-free state.

CONSTITUTION: In the application to the device for playing or sporting by suspending a person onto a balloon, a harness 13 is suspended through a supporting rope 12 onto a balloon 11 in which the lightweight gas and the heavy gas are introduced according to the necessity inside. One edge of a safety rope 14 is fixed onto the harness 13, and the other edge is wound onto a winch 15 mounted onto a transfer dolly 16. A buoyancy adjusting chamber 18 is installed at the lower part of the balloon 11, and the buoyancy of the balloon is balanced with the body weight of a passenger who is fixed onto the harness 13 by adjusting the quantity of the lightweight gas such as helium gas which charges the inside. The quantity of the lightweight gas is adjusted after connecting the inlet valve 31 of the balloon 11 with a buoyancy adjusting device 17 installed on the ground.