Software Process Improvement(SPI) has been a challenging issue to software organizations. The factors affecting SPI were analysed for improving software development processes. Numerous studies suggested influencing factors, and assessment models were utilized for software improvement. This research suggested that SPI factors affecting on an organizational performance may vary according to the CMM(Capability Maturity Model) level. The moderating effects of organizational maturity level between the SPI factors and the organizational performance were empirically tested. This research found that all six SPI factors except for the resistance to change affected the organizational performance. The moderating effects of management support, goal alliances, participation, and effect analyses were empirically supported. These results can provide several implications or a practical guidance to academic and industry professionals.