There is provided a highly reliable semiconductor light emitting element and vehicle lighting unit as well as associated methods. The semiconductor light emitting element can include a support substrate, a semiconductor stacked body including a first semiconductor layer of a first conductivity type, an active layer formed on the first semiconductor layer, and a second semiconductor layer of a second conductivity type formed on the active layer. The element can further include a bonding layer configured to bond the support substrate and the semiconductor stacked body, the bonding layer having a side surface that forms an angle exceeding 90° with a surface of the bonding layer on the side of the semiconductor stacked body, and an interconnection layer configured to extend from the upper surface of the semiconductor stacked body to cover the side surface of the bonding layer.