A gear change control device and a method for a work vehicle for reducing a heat quantity generated by gear shift clutches of a transmission and a gear shift shock to reduce a load on the clutches without inducing elongation of a cycle time or deterioration of a work efficiency. A clutch pressure (Pm) of an input clutch(10) is reduced to switch from a connected state to a power-transmittable sliding state at a time (tE) after a time (tA) at which a cut-off operation of a gear shift clutch used before gear shifting (reverse clutch 22) is started and before a time (tD) at which the connecting operation of a selected gear shift clutch to be used after the gear shifting (forward clutch 21) is completed.