We present the results of CO observations of the flocculent spiral NGC 5055 with the Nobeyama 45-m telescope. A long and symmetric two-arm spiral structure was found in the galaxy. Since the molecular arms are coincident with those of old stars seen in the K'-band, they are caused by a stellar density wave. The molecular spiral arms can be fitted with a logarithmic spiral with a pitch angle of 19(deg) , which is comparable to that measured in M51. The arm-to-interarm ratio is 2--3 (R = 80''--160'') and increases with the galactocentric radius. Since bright HII regions also distribute along the molecular gas, massive star formation occurs in the arms. These results indicate that the flocculent spiral structure of NGC 5055 can not be explained solely by stochastic star formation.