A light head, light device, assembling method of light head and light device are provided. The light device includes a light head and a third unit. The light head includes a first unit, a second unit, a cable, a fixing sheet, a first pin, a conducting sheet, and multiple second pins. The first unit has a side surface, a bottom surface, a pair of slots, and a protrusion portion. The slots are on the bottom surface. The second unit encircling the first unit exposes the protrusion portion. The fixing sheet electrically connected to a first conducting terminal of the cable is inserted into the slots. The first pin inserts into the protrusion portion to make the cable contact the first pin and the protrusion portion. The conducting sheet is under the second unit. The second pins make the conducting sheet, the first and second units assembled together.