This paper proposes the PWSCC growth assessment methodology for Alloy 600 steam generator tubes based on the PWSCC initiation model and finite element damage analysis. Damage was defined integral ratio of the operating time increment to the PWSCC initiation time. The Garud's PWSCC initiation model considering temperature, water chemistry, material, and cold working effects was used to calculate the PWSCC initiation time in the damage. The assessment methodology was calibrated and verified comparing with the JNES's PWSCC growth test results for the single-cracked steam generator tube. The verified methodology was applied to collinear and parallel axial surface cracks. As a result, for the collinear crack, the penetration times of the collinear cracks are earlier than those of the single cracks, the penetration time increases with increasing the space between adjacent cracks, and the penetration occurs before the coalescence for the case that two cracks are more distant than the specific space. For the parallel crack, the penetration times of the parallel cracks are later than those of the single cracks, and the penetration time increases with decreasing the space between adjacent cracks.