A mercury-free vehicle discharge lamp is described as including a discharge space with electrodes, wherein a spherical length b, which is a length in a tube axial direction of the light emitting part is 7.5 mm to 8.5 mm and a thickness volume V of the light emitting part is 50 mm3 to 100 mm3, and wherein the following formula is satisfied: −20≦(a−35)×5.5+(x−13.5)×10 +(1.85−t)×100+(2.5−d)×100≦20, a: power W supplied in a stable lighting time, x: pressure [atm] of rare gas sealed in the discharge space ranging 10˜17 atm, t: thickness [mm] of a part where a wall with maximum thickness and ranging 1.30˜1.85 mm, and d: inner diameter [mm] of a part where the wall with maximum thickness.