A light bulb apparatus includes a bulb shell, a bulb head and a light source module. The bulb shell has a light passing portion and a neck portion. The neck portion has a first protruding ring, a first gap ring and a second protruding ring. The bulb head has a body portion and a cap portion. The neck portion has a third protruding ring, a second gap ring and a fourth protruding ring. The first protruding ring is placed in a second concave structure, the fourth protruding ring is placed in a first concave structure. The light source module is enclosed by the bulb shell and emitting light passing through the light passing cover of the bulb shell.