Body velocity estimating device 10A is constituted by acceleration measurement unit 11, acceleration separation unit 12, filter processing operation unit 13, acceleration addition unit 14, integration processing operation unit 15, and estimated body velocity output unit 16. The unit 12 compares an acceleration measured by the unit 11 with set acceleration upper and lower limit reference values to separate the measured acceleration into reference value range-in and range-out accelerations. The unit 13 performs filtering on the separated reference value range-out acceleration to calculate filtered accelerations of the reference value range-out acceleration. The unit 14 adds the filtered accelerations to the previously separated range-in acceleration. The unit 15 multiplies the added acceleration by an operation period, and adds the resultant to the estimated body velocity calculated in the preceding one operation period to update the value of the estimated body velocity. The unit 16 outputs the updated estimated body velocity.