A lighting device for a hand tool contains: a base, an illumination unit, and a clamping mechanism. The illumination unit is disposed in the base which includes a lighting orifice and four projections, each two of which are arranged on each of two sides of a bottom end of the base, and between each two projections is defined a V-shaped groove. The clamping mechanism includes a retainer, a connection shaft, and a resilient element, wherein the retainer has a fitting portion, a positioning section, and a controlling section, and wherein the positioning section is placed on the bottom end of the base and is defined among the four projections, the controlling section extends out of one side of the base, and the resilient element is fitted on the connection shaft and has a first end abutting against the base and a second end contacting with the controlling section.