PROBLEM TO BE SOLVED: To provide a method and apparatus for measuring an outer surface shape of an electric resistance welded steel pipe after cutting a weld bead of an electric resistance welding.SOLUTION: The method for measuring outer surface shape of an electric resistance welded steel pipe comprises: vertically irradiating a prescribed-width area including a bead cut area 9 of the electric resistance welded steel pipe and right/left steel pipe base materials with slit-like laser beam 12 from above the bead cut area 9 in such a manner that the direction of the slit-like laser beam 9 becomes orthogonal to the bead cut part 9; performing arithmetic processing on an image 14 obtained by observing the slit laser beam 12 from obliquely above the bead cut part 9 to acquire a shape of the prescribed-width area including the bead cut part 9 and the right/left steel pipe base material, a screw down trace of an upper squeeze roll, and a screw down trace of the upper squeeze roll with sputters attached thereto.
