A sprinkler side frame coupling device including: a side frame coupled to support frames each having a locking step formed on top thereof and having a body, first bending portions formed on both sides of the body, a horizontal portion formed from each first bending portion, a second bending portion, a space portion formed on each first bending portion, pin support portions, long holes formed on the pin support portions, shaft support portions, and inclined projection portions; a locking pin having a shape of ‘U’ fitted to the long holes; and coupling members each having a plurality of inclined teeth.