A form equipped with a concrete paste outflow prevention device is provided to prevent concrete paste from being leaked to a floor by prevent gap between the floor and the form when the form is installed. A form equipped with a concrete paste outflow prevention device comprises: a pair of main frames(110); an upper reinforcement frame and a lower reinforcement frame being formed in the upper and lower parts of the main frame and intensifying solidity; a stopper cover(130) adhering closely to the lower reinforcement frame; a plurality of pre-fastening holes formed in the stopper cover; a reinforcement cover(140) coupled in the lower surface of the stopper cover; a post-fastening hole(142) formed in the reinforcement cover; a cushion member(150) which is inserted between the stopper cover and the reinforcement cover and in which a through-hole is formed; and a rivet(160) integrally coupling the cushion member to the stopper cover and the reinforcement cover.
