To recover fish habitats and restore rich biota in rural areas, we evaluated the habitat potential for field gudgeon Gnathopogon elongatus elongatus, a representative species in rural areas, in non-improved drainage canals with soil and improved drainage canals having concrete walls but with a soil bottom in Yatsu paddy fields of the Shitada-gawa River basin, Chiba Prefecture, Japan, using habitat suitability indexes (SI). SI relations for water depth, water velocity, water width, substrate, and vegetation covering for life stages of the fish were developed using field research data collected from July 2002 to June 2004. The composite suitability indexes SI_depth × SI_substrate × SI_width (larvae), SI_depth × SI_velocity × SI_width (juvenile) and SI_depth × SI_substrate × SI_vegetation (adult) were adopted statistically for calculation of the habitat potential (HP), expressed by a dimensionless weighted usable area. The values of HP varied monthly, but did not show significant differences between non-improved and improved canals for all life stages. This result showed that the improved canals were not inferior in producing fish habitats when compared with the non-improved canals. Also, it was clarified that the improved canals could even be used as alternative habitats to give temporary refuge to the fish, when a canal in this basin was being modified.