A planetary gear train includes a carrier having a first side plate, a second side plate disposed in parallel to the first side plate and pinions rotatably supported by the first and second side plates; and a ring member secured to an outer edge of the second side plate. The first side plate has a plurality of first convex portions whose edge portion form an outer edge and a plurality of first concave portions formed between adjacent first convex portions. The second side plate has a plurality of second convex portions whose edge portion form an outer edge and whose width in a peripheral direction is wider than the first convex portion, and a plurality of carrier bridges axially extended from a part between the plurality of second convex portions to the plurality of first concave portions and secured to the first concave portion.