In an acceleration estimation device for estimating acceleration of a
vehicle, a Karman filter for a constant speed estimates x-direction
acceleration offset and z-direction acceleration offset when a motorcycle
is stopped and is traveling at constant speed. An offset storage stores
an x-direction acceleration offset estimated value and a z-direction
acceleration offset estimated value. An offset corrector corrects an
x-direction acceleration and a z-direction acceleration on the basis of
the x-direction acceleration offset estimated value and the z-direction
acceleration offset estimated value when the motorcycle is accelerated
and decelerated. A Karman filter for acceleration/deceleration estimates
the pitch angle of a vehicle body when the motorcycle is accelerated and
decelerated. An acceleration corrector obtains an X-direction
acceleration and a Z-direction acceleration on the basis of the estimated
pitch angle. A vehicle speed operation unit integrates over time the
X-direction acceleration to calculate an X-direction speed.