A propylene block copolymer, a process for preparation of the propylene block copolymer, and a propylene resin composition comprising the propylene block copolymer. The propylene block copolymer comprises (a) from 35 to 95% by weight of a polypropylene block and (b) from 10 to 65% by weight of a block of a copolymer of a propylene and other .alpha.-olefins, the propylene block copolymer having: (i) in a crystallization temperature curve determined by a differential scanning calorimeter, besides a main peak, secondary peaks in a temperature range of from 90.degree. to 100.degree. C., and a proportion of the area of the secondary peaks to that of a main peak of from 1.5 to 10%; and (ii) a relationship between an amount of a soluble content on xylene extraction at 25.degree. C. and a proportion of the area of the secondary peaks to that of the main peak represented by equation (I): 0.1X.sub.IS -1.ltoreq.SMA (I) wherein X.sub.IS represents an amount of a soluble content on xylene extraction at 25.degree. C. in terms of percent by weight; and SMA represents a proportion of the area of the secondary peaks to that of the main peak in terms of percent.