A printed circuit board assembly includes a first printed circuit board with first surface and second surface with a slit portion and a second printed circuit board with third surface and fourth surface with a first end portion and a second end portion. The first end portion is fitted in the slit portion and a tip of the first end portion protrudes from the second surface. The first printed circuit board includes first electrodes arranged along the slit portion in a longitudinal direction of the slit portion on the second surface. The second printed circuit board includes second electrodes arranged in the first end portion on the third and fourth surfaces. The second electrodes are joined to the first electrodes with solder. The first printed circuit board includes a support fixed to the first surface. The second printed circuit board is attached to the support by an adhesive substance.