Surface hardening treatment by laser beam was applied to austempered spheroidal graphite cast iron (ADI) bar specimens 30 mm in diameter, and wear characteristics in dry slip-rolling contact conditions were investigated based on the irradiating conditions of the laser. When laser beam was irradiated on the surface of the ADI bar, remelting and the corresponding rapid cooling took place, and the remelted zone (RZ) resulted in the formation of a mixture of retained austenite and eutectic carbide structure of which Vickers hardness was about 600 HV. The microstructure of the heat affected zone (HAZ) formed around the RZ transformed into martensite with high hardness (850-950 HV) from the ausferrite of the as-austempered structure of about 600 HV. But when the number of laser irradiations on the bar exceeded 90, the irradiation spacing became so narrow that the neighboring HAZ overlapped with each other, resulting in decreased HAZ hardness to about 600 HV because the HAZ transformed into tempered-martensite by tempering. While the number of laser irradiations increased up to 120 on the bar, wear loss decreased remarkably. However, when the number of irradiations exceeded 120 on the bar, wear loss increased with increasing number of irradiations. The wear loss of ADI was minimum when the number of irradiations was 120, and decreased to 60% of ADI without irradiation. The surface hardening treatment by laser irradiation is concluded to be very effective for improving the anti-wear characteristics of ADI, and its wear characteristics are found to be influenced largely by the area rate of RZ and HAZ on the surface.