Laser welding device and laser welding method

Abstract

A laser welding device () for welding a weld part () with laser light (L) includes: a laser emitting head () overlapping the laser light (L) and a measurement light (S) coaxially with each other and applying the laser light (L) and the measurement light (S) to the weld part (), the measurement light (S) having a wavelength different from a wavelength of the laser light (L); a first parallel plane plate and a second parallel plane plate, changing an irradiation position of the measurement light (S) such that the irradiation position orbitally move around a center of rotation that moves on a predetermined welding path in a radius of rotation that is smaller than ½ of a spot diameter of the laser light (L); a measuring instrument () repeatedly measuring a weld penetration depth of the weld part () based on the measurement light (S) that is emitted from the laser emitting head () and is reflected on the weld part () while the measurement light (S) is being orbitally moved; and a determiner () determining the weld penetration depth of the weld part () using a plurality of measured values of the weld penetration depth, the plurality of measured values being measured by the measuring instrument () within a fixed time period while shifting a start time point of the fixed time period.