System for inspecting defects of panel device includes a to-be-inspected device, a platform for holding the to-be-inspected device, a power unit, and a light source apparatus. The light source apparatus is controlled by the power unit to provide an inspection light to the to-be-inspected device for inspecting whether or not having defects. The light source apparatus includes a cathode structure, an anode structure, a fluorescent layer, and a low-pressure gas layer. The fluorescent layer is located between the cathode structure and the anode structure. The low-pressure gas layer is filled between the cathode structure and the anode structure, for inducing the cathode to emit electrons uniformly. The low-pressure gas layer has an electron mean free path, allowing at least enough electrons to directly hit the fluorescent layer under an operating voltage.