An electronic component unit applicable to a wire harness includes: a plurality of blocks each including at least one main body portion to each of which an electronic component is attached, the blocks each including block-side joints for joining any two of the blocks to each other, the blocks being joined together via the block-side joints with the main body portions arranged side by side in a first direction with gaps between adjacent ones of the main body portions; and a supporting wall body including a plurality of wall-body side joints for supporting and fixing in a second direction intersecting the first direction, in a cantilever fashion, the blocks joined together via the block-side joints.