In chapter 1, we mentioned `outflows' ejected from the protostars and pre-main-sequence stars. L1551 IRS5 is a typical example which shows a number of outflows are ejected in the course of star formation. One is molecular outflow, whose lobes extends in two opposite directions from the IRS-5 (Snell et al 1980). This is traced by CO emission line. They estimated an expansion velocity of the CO gas of , a mass of 0.3 . The dynamical age is equal to . Inside the CO outflow lobe, several Herbig-Haro objects are found, which are emission-line nebulosities. Proper motion studies have revealed the motion of such H-H objects. Cudworth & Herbig (1979) reported HH28 and 29 have , which corresponds to . In a neighbor of the IR source a stellar jet is found (Mundt & Fried 1983) by optical emission lines. Its size is equal to and the jet indicates rather well-collimated shape (the opening angle ). The relationship between these two outflows (massive molecular outflow and less massive optical jet) are not clear yet.