A vehicle speed calculating device is provided. The device includes a first vehicle speed calculating module configured to calculate a first vehicle speed based on a vehicle speed pulse count of a vehicle, a second vehicle speed calculating module configured to calculate a second vehicle speed based on positioning signals broadcasted from positioning satellites, an acceleration acquiring module configured to acquire an acceleration detected by an acceleration sensor provided to the vehicle, an estimating module configured to estimate a speed error based on a correlative relationship of a difference value between the first and second vehicle speeds with the acceleration, and a correcting module configured to correct the first vehicle speed based on the speed error.