The invention discloses a steel plate 
butt welding gap adjusting device, and belongs to steel plate position adjusting devices. The problem that according to an existing steel plate 
butt welding positioning device, the 
butt welding steel plate gap is difficult to precisely adjust is solved. The device comprises a base 
assembly, a fixing 
assembly, a transmission mechanism, a positioning mechanism and a gap indicating 
assembly; the base assembly comprises a bottom plate, a front guide rail and a rear guide rail; the fixing assembly comprises a left fixing plate, a right fixing plate, a left pressing plate and a right pressing plate; the transmission mechanism comprises a transmission shaft, a reverse shaft, a front screw and a rear screw; the positioning mechanism comprises a left 
camshaft, a right 
camshaft, a left long positioning sliding block, a right long positioning sliding block, a left short positioning sliding block, a right short positioning sliding block, a left pressing strip, a right pressing strip, a 
left shifting fork, a right shifting fork, a left driving rod, a right driving rod and a positioning pin; the gap indicating assembly is composed of a left pointer, a right pointer and a ruler; the device is simple in structure, low in manufacturing cost, small in work environment influence, easy and convenient to operate, capable of ensuring the steel plate butt 
welding gap and precise positioning and greatly improving the 
welding quality and the 
welding efficiency and suitable for multiple welding processes of lasers, electric arcs and the like.