Musk melon is the favorite fruit with a high market value in Japan, and the fragrance is one of the major factors determining the fruit quality of melon. In this study, mutant melon hairy roots which had been induced by means of the T-DNA insertion mutagenesis were found to produce volatile compounds with the fruity fragrance of mature melon. The volatile compounds were extracted and identified by GLC-mass spectrometry. Some essential oils such as (Z)-3-hexenol, (E)-2-hexenal, 1-nonanol, and (Z)-6-nonenol were stably synthesized by these hairy roots despite the increased number of subcultures. The productivity of these compounds by the best hairy root line was shown to be considerably higher than naturally ripened melon fruits.