The present disclosure relates to a flap fixing buckle including: a plug member having a cross bar that transverses an intermediate portion of a loop-shaped frame, in which a coupling protruding portion in which a magnet is embedded protrudes from the cross bar; and a socket member having a coupling groove into which the coupling protruding portion is inserted and which is formed in an upper surface of the socket member, in which a magnet is embedded inside the coupling groove, and a wing portion extends at the periphery of the upper surface of the socket member, and as a result, when the flap fixing buckle is installed on a bag or the like, an aesthetic external appearance may be formed because of a simple configuration, and the flap fixing buckle may be stably and conveniently fastened.