A safety light is mounted retractably in a handlebar of a bicycle and has a housing, a retaining clamp, a sleeve, a lamp assembly and a spring. The retaining clamp is mounted in the housing. The sleeve is mounted around the housing. The lamp assembly is mounted slidably in and selectively protrudes from the housing and comprises a lamp housing, a retaining post and a light assembly. The lamp housing is mounted slidably in the housing and has an inner end, an outer end and at least one lamp hole. The retaining post is formed on the inner end the lamp housing and is engaged by the clamp. The light assembly is mounted in the lamp housing and comprises a circuit board and at least one lamp. The at least one lamp is mounted on the circuit board. The spring is mounted between the lamp assembly and the retaining clamp.