To detect an approaching state of an upper body to a front vehicle body member regardless of a seat fore-and-aft slide position, by avoiding damaging property without lowering protecting performance.

The seat slide device is made as a downward placing structure supported by a lower side, and a layout structure of a load sensor 14 is specified. As a total sum of smoothing data by smoothing processing about each of specific plural values calculated on the basis of load information from the load sensor 14, a load is calculated and recognized. When the load is determined as not less than a seating load of a child, a gravity center position CG/P is calculated and specified on the basis of the load. When the gravity center position is determined as exceeding a distance threshold value to a front side as compared with the distance threshold Th4 previously set as a specific distance from a predetermined base point (14-#2), the seating posture is determined as an abnormal approaching posture to an instrument panel 26, and after than, determination and selection of a load zone is avoided.