A dezincification plant, being used in a hydrometallurgical method for nickel oxide ore, the dezincification step being such that a sulfurization treatment is applied to a post-neutralization solution obtained through a neutralization step of neutralizing a leachate of said nickel oxide ore thereby to form zinc sulfide, and said zinc sulfide is separated to obtain a mother liquor containing nickel and cobalt for nickel recovery, the dezincification plant comprising: a dezincification reaction tank configured to form zinc sulfide by applying a sulfurization treatment to the above-mentioned post-neutralization solution and form a mother liquor containing said zinc sulfide for nickel recovery; a filter apparatus configured to separate the above-mentioned zinc sulfide and the above-mentioned mother liquor for nickel recovery; and a storage tank configured to temporarily store the above-mentioned zinc-sulfide-containing mother liquor for nickel recovery, while to have flow piping installed thereby to transfer said zinc-sulfide-containing mother liquor for nickel recovery to the above-mentioned filter apparatus, the flow piping being coupled to transfer piping connected to said filter apparatus, wherein the above-mentioned flow piping installed in the above-mentioned storage tank is coupled to circulation piping at a coupling portion coupled to the above-mentioned transfer piping, and branched, and a switching valve is installed at said branch point, furthermore, a measurement portion to measure a flow rate and/or a temperature of a solution flowing through the above-mentioned flow piping is provided to said flow piping, and in start-up of the dezincification plant after completion of a periodic inspection, at a time of starting the start-up, without applying a sulfurization treatment to the above-mentioned post-neutralization solution, said post-neutralization solution is controlled by adjustment of the above-mentioned switching valve so as to be circulated to the above-mentioned dezincification reaction tank via the above-mentioned circulation piping coupled to the flow piping installed in the above-mentioned storage tank, and, when a flow rate and/or a temperature of the post-neutralization solution circulated reach a predetermined value or more, a sulfurization treatment is applied to the post-neutralization solution in the dezincification reaction tank thereby to form a zinc-sulfide-containing mother liquor for nickel recovery, and said zinc-sulfide-containing mother liquor for nickel recovery is transferred to the above-mentioned filter apparatus via the above-mentioned transfer piping by adjustment of the above-mentioned switching valve. a dezincification reaction tank configured to form zinc sulfide by applying a sulfurization treatment to the above-mentioned post-neutralization solution and form a mother liquor containing said zinc sulfide for nickel recovery; a filter apparatus configured to separate the above-mentioned zinc sulfide and the above-mentioned mother liquor for nickel recovery; and a storage tank configured to temporarily store the above-mentioned zinc-sulfide-containing mother liquor for nickel recovery, while to have flow piping installed thereby to transfer said zinc-sulfide-containing mother liquor for nickel recovery to the above-mentioned filter apparatus, the flow piping being coupled to transfer piping connected to said filter apparatus,