Mineral ore slurry pretreatment method, and method for manufacturing mineral ore slurry

Provided is a method by which it is possible, in a wet-process method for refining nickel oxide ore, to efficiently reduce the amount of acid used in the leaching step and the amount of neutralizing agent used in the final neutralization step without lowering the nickel recovery. The mineral ore slurry pretreatment method pertaining to the invention is a mineral ore slurry pretreatment method that involves subjecting nickel oxide ore to a leaching step in a wet-process refining method, wherein the method comprises: a first separation step for separating a mineral slurry into a coarse-grained portion and a fine-grained portion using, in one to three stages, a hydrocyclone and/or a density separator, and subjecting the fine-grained portion to a leaching treatment; a second separation step for separating the coarse-grained portion separated in the first separation step into a heavy-specific-gravity portion and a light-specific-gravity portion using at least a spiral concentrator, and subjecting the heavy-specific-gravity portion to a leaching process; and a vibration sieving step for separating the light-specific gravity portion separated in the second separation step into an oversize fraction and an undersize fraction by means of vibration sieving, and subjecting the undersize mineral slurry to a leaching process.