Five external morphometric characters and size at maturity in carapace width of the swimming crab, Protunus sanguinolentus, were examined and compared between sampling groups obtained from the Keelung Shelf and Taiwan Bank. The external morphometric characters used in the present study are: carapace width, carapace length, distance between two sides of first spine, fifth abdominal segment width, fifth abdominal segment length, chela length, chela width and movable dactylus length. Two statistical approaches were applied, i.e. multivariate morphometric analysis was used to compare external morphometric characters and a likelihood ratio test was used to compare maturity curves. Both results obtained show significant differences between the two sampling groups. The size at maturity was represented by LM₅₀ and estimated theoretically from maturity curves, indicating that LM₅₀ for females is 97.00 mm CW in Keelung Shelf, and 82.36 mm CW in Taiwan Bank, whilst for males it is 92.62 mm CW in both areas. The results of statistical comparisons are coincident that external morphometric characters of female Protunus sanguinolentus between the waters off the Keelung Shelf and the Taiwan Bank are significantly different.