A shower door adjusting device, comprising: a first side frame and a second side frame, one of the first side frame and the second side frame is a fixed side frame and the other of the first side frame and the second side frame is an adjustable side frame; a first fixing base assembly including a first fixing base and a second fixing base, wherein the first fixing base is fixed on the first side frame, the second fixing base is detachably fixed on the first fixing base, an installation groove is formed between the first and second fixing bases (12,14), and the first fixing base assembly is provided with a first through hole therein; a locking sheet having an end provided with a boss, wherein the end of the locking sheet is installed in the installation groove, the locking sheet is provided with a first locking hole which faces the first through hole, a spring abutting against the boss is provided in the first fixing base assembly, the boss is provided with a threaded hole, a screw passing through the threaded hole is provided to the first fixing base assembly, and one end of the screw close to the first fixing base is provided with an abutting portion; and a first connecting bar fixed to the second side frame and provided with a first rack passing through the first locking hole and the first through hole, wherein the first rack is locked within the first locking hole after the abutting portion of the screw abuts against the first fixing base; wherein: a top wall of the second fixing base is provided with a through hole, through which one end of the screw passes and which is in the shape of an inverted taper. a first side frame and a second side frame, one of the first side frame and the second side frame is a fixed side frame and the other of the first side frame and the second side frame is an adjustable side frame; a first fixing base assembly including a first fixing base and a second fixing base, wherein the first fixing base is fixed on the first side frame, the second fixing base is detachably fixed on the first fixing base, an installation groove is formed between the first and second fixing bases (12,14), and the first fixing base assembly is provided with a first through hole therein; a locking sheet having an end provided with a boss, wherein the end of the locking sheet is installed in the installation groove, the locking sheet is provided with a first locking hole which faces the first through hole, a spring abutting against the boss is provided in the first fixing base assembly, the boss is provided with a threaded hole, a screw passing through the threaded hole is provided to the first fixing base assembly, and one end of the screw close to the first fixing base is provided with an abutting portion; and a first connecting bar fixed to the second side frame and provided with a first rack passing through the first locking hole and the first through hole, wherein the first rack is locked within the first locking hole after the abutting portion of the screw abuts against the first fixing base; wherein: a top wall of the second fixing base is provided with a through hole, through which one end of the screw passes and which is in the shape of an inverted taper.