Activation control apparatus and method of airbag apparatus

A satellite sensor (16) and a floor sensor (14) are provided in a forward portion and a central portion, respectively, of a vehicle body. A calculated value and a speed are determined through predetermined processing of a deceleration detected based on an output signal of the floor sensor (14). If a value determined from the relationship between the calculated value and the speed exceeds a predetermined threshold changing pattern, an airbag apparatus is activated. The threshold changing pattern is set by selecting a map from a Hi map, a Lo1 map, a Lo2 map and a Lo3 map based on a deceleration determined from an output signal of the satellite sensor (16). If a map different from the current map is to be set as a threshold changing pattern, the threshold changing pattern is set to the desired map after a state that allows the map to be set continues for a time corresponding to a difference between the two maps.