The composition of the volatile components from unripe (I) and ripe (II) Japanese apricot (Prunus mume Sieb. et Zucc.) have been investigated. Seventy-six volatile components were identified, 25 for the first time as volatile constituents of Japanese apricot. The main components were benzaldehyde (I, 59.16%; II, 1.81%), isolongifololyl acetate (II, 19.21%), palmitic acid (I, trace; 10.22%), linalool (I, 9.93%; II, 7.34%), and butyl acetate (II, 8.30%). Unripe Japanese apricot have a green colour due to the main components being aldehydes. On the contrary, ripe Japanese apricot had a fruity note due to the increase of the ratio of esters during ripening.