In the serpentine area in Hokkaido, 46 taxa of serpentine plant species were recognized, and 44 of them were endemic to Hokkaido. The P concentration in the serpentine plants was lower, while the concentrations of K, Ca, and N were higher, than those in nonserpentine plants and trees. The Ni concentration of the serpentine plants increased proportionally to that of the exchangeable Ni concentration in the soil up to 10 mg kg^-1 soil, but did not increase further. Among the plants investigated, a nonserpentine plant, Thlaspi japonicum, was recognized for its extraordinary Ni accumulation (1300 mg kg^-1 on average), indicating that this plant is the first Ni-hyperaccumulator identified in Japan.