A welded portion inspection method for inspecting a welded state of a welded portion formed when a plurality of workpieces are welded, the method comprising: a first irradiation step of irradiating the workpieces (W1, W2) with welding laser light along a weld trajectory set on the workpieces (W1, W2) for welding the workpieces (W1, W2); a second irradiation step of irradiating the workpieces (W1, W2) with inspection laser light along a scan trajectory set in a molten portion of the workpieces (W1, W2) melted by the first welding laser light; a light receiving step of receiving emitted light emitted from the workpieces (W1, W2) due to the irradiation of the workpieces (W1, W2) with the welding laser light and the inspection laser light during a period from the welding laser light irradiation in the first irradiation step to the end of the second irradiation step; and an inspection step of inspecting the welded state of the welded portion based on an intensity waveform of the received emitted light, wherein: during transition from the first irradiation step to the second irradiation step, the welding laser light irradiation is interrupted and then the laser light with which the workpieces (W1, W2) is irradiated is switched to the inspection laser light; characterized in that in the inspection step, two points in time at which the emitted light intensity is equal to or less than a certain threshold value are extracted from the intensity waveform of the emitted light as an inspection start point in time and an inspection end point in time, a period from the inspection start point in time to the inspection end point in time is estimated as being an irradiation period of the inspection laser light irradiation, and the welded state is inspected based on the intensity waveform of the emitted light in the irradiation period. a first irradiation step of irradiating the workpieces (W1, W2) with welding laser light along a weld trajectory set on the workpieces (W1, W2) for welding the workpieces (W1, W2); a second irradiation step of irradiating the workpieces (W1, W2) with inspection laser light along a scan trajectory set in a molten portion of the workpieces (W1, W2) melted by the first welding laser light; a light receiving step of receiving emitted light emitted from the workpieces (W1, W2) due to the irradiation of the workpieces (W1, W2) with the welding laser light and the inspection laser light during a period from the welding laser light irradiation in the first irradiation step to the end of the second irradiation step; and an inspection step of inspecting the welded state of the welded portion based on an intensity waveform of the received emitted light, during transition from the first irradiation step to the second irradiation step, the welding laser light irradiation is interrupted and then the laser light with which the workpieces (W1, W2) is irradiated is switched to the inspection laser light; characterized in that in the inspection step, two points in time at which the emitted light intensity is equal to or less than a certain threshold value are extracted from the intensity waveform of the emitted light as an inspection start point in time and an inspection end point in time, a period from the inspection start point in time to the inspection end point in time is estimated as being an irradiation period of the inspection laser light irradiation, and the welded state is inspected based on the intensity waveform of the emitted light in the irradiation period.