The invention discloses a wallboard connecting device. The wallboard connecting device comprises a connecting piece, wherein the connecting piece comprises a first connecting board, a second connecting board and a third connecting board which are connected in sequence; a long strip-shaped connecting groove is formed in the second connecting board; the first connecting board and the third connecting board are respectively provided with a waterproof board; the vertical distance between one side of one waterproof board and one side of the other waterproof board which are far away from the second connecting board is larger than the vertical distance between the first connecting board and the third connecting board; a second clamping board is provided with a clamping bulge; the clamping bulge is clamped in the connecting groove; the inner surface of a first clamping plate leans against the outer surface of the first connecting board; the inner surface of the second clamping board leans against the outer surface of the second connecting board; the inner surfaces of a first folding board and a second folding board respectively lean against the outer surfaces of two buckling boards. According to the wallboard connecting device provided by the invention, the installation labor intensity of a wallboard is reduced, the installation efficiency of the wallboard is increased, a fixing function of the connecting piece is added, a waterproof function is added, and the use convenience of a user is increased.