In Taiwan, the b values of earthquakes with focal depths of less than 35 km are smaller offshore than on land. On land, except for the Coastal Range, the b value correlates to the degree of metamorphism of rocks, which decreases inland from east to west. Small b values appear at the leading edge of the subducting slab of the Philippine Sea plate that plunges underneath northern Taiwan, possibly indicating high stress due to a bending of the slab. Large b values in an area including the volcano groups in northern Taiwan may be due to the remnant geothermal effect after past volcanic activities. Besides, small b values on land are mainly associated with low Bouguer gravity anomalies; offshore, small b values are related to high Bouguer gravity anomalies, particularly in regions with a large gravity gradient.