PURPOSE: An apparatus is provided to automatically inject connecting sheets having various thicknesses into a welding equipment of a strip recoiling line in the state that the connecting sheets are adjusted to proper thicknesses so as to continuously weld strips having different thicknesses. CONSTITUTION: In an apparatus(1) for injecting connecting sheets(S) into a welding line(P) to continuously weld preceding and following strips(10,20) in a recoiling line, the apparatus for automatically supplying the connecting sheets into the continuous strip welding line comprises a sheet injection part(30) which is equipped with a sheet adsorption pipe(32) that is installed at the upper part of one side of the line(P) in such a way that the adsorption pipe(32) is ascended or descended and moved back and forth so as to inject the connecting sheets(S) into the line(P); and a sheet storage part(90) consisting of a storage means(60) storing the connecting sheets(S) having a plural thicknesses so that an appropriate sheet(S) is supplied by the adsorption pipe(32) according to a thickness difference between the preceding and following strips(10,20), and a sheet moving means(70) for moving the sheets(S) from the storage means(60) to an adsorption position.