To provide a flow improver for slurry and a flow improving method which improve effectively the liquid viscosity characteristics of an inorganic slurry and therefore ensure a stable slurry conveyance even when a solid content concentration changes, and contrive to curtail a power for the slurry conveyance.

The flow improver for an inorganic slurry is characterized by containing aldonic acid and/or a salt of aldonic acid. The flow improving method in a process of transferring the slurry having a principal component of an inorganic matter is characterized by adding aldonic acid and/or a salt of aldonic acid to the slurry. The existence of a hydroxymethyl group and a carboxyl group at the both ends of the main chain of aldonic acid or that of a hydroxymethyl group and a carboxyl group at the both ends of the main chain of a salt of aldonic acid takes a specific improvement effect on a liquid viscosity characteristics.