A method for manufacturing a slurry for a positive electrode of a nonaqueous electrolyte secondary battery using an aqueous solvent containing an alkali metal complex oxide, includes: while causing a raw material slurry containing a solid content and the solvent as slurry raw materials for a positive electrode of the nonaqueous electrolyte secondary battery to flow along a path, performing a neutralization treatment on an alkali component in the raw material slurry by inorganic carbon supplied to the raw material slurry flowing along the path.