Lock mechanism for seat slide device and assembling method thereof

A seat slide device includes a lock mechanism (18) swingably supported to a bracket and having a lock piece (5) with lock pawls (4) rotatively biased by a coil spring (14) and engaged/disengaged from lock openings of a lower rail, a spring protrusion (11) formed with the bracket (6) and catching one end (14a) of the coil spring (14), a lock releasing lever (12) formed with the lock piece (5) and catching another end (14b) of the coil spring (14), and a provisional spring protrusion (13) formed with the lock piece (5) and located in the neighborhood of the spring protrusion (11) and catching one end (14a) of the coil spring (14) provisionally.