Method for producing resin part

A method for producing a resin part, the method comprising:

• preparing an intermediate body comprising a first member and a second member, the first member containing a resin;
• and
• welding the first member with the second member by performing scanning of the intermediate body with a first laser beam and a second laser beam, wherein:
• when a first spot is defined as a spot of the first laser beam on a front surface of the intermediate body and a second spot is defined as a spot of the second laser beam on the front surface of the intermediate body:
• in the welding of the first member with the second member, the scanning with the first laser beam and the second laser beam is performed in a state in which a center of the second spot is located on a rear side in a direction of the scanning with the first laser beam and the second laser beam as compared to a center of the first spot while at least a part of the first spot and at least a part of the second spot overlap with each other, and
• at least one of the first spot and the second spot has a maximum length in a direction parallel to the direction of the scanning longer than a maximum length in a direction perpendicular to the direction of the scanning.