Abstract: A headlight apparatus including a lamp body having a recess being open in the front direction and a lens covering the front opening of the recess, and a reflective mirror tiltably mounted on the lamp body. Two spaced apart adjust shafts are respectively supported rotatively on the lamp body with the rear end portions thereof projecting from the rear surface of the lamp body, and screw-thread portions are formed respectively on the front portions of the adjust shafts to engage with nuts respectively. The nuts have respectively on the outer side surfaces resilient retaining pieces for snappingly engaging with respective mounting members which are mounted on the reflective mirror. A ball joint connection is formed between the reflective mirror and the lamp body at the position spaced apart respectively from respective adjust shafts.