The present invention enables simple production of osmium tetroxide having comparable performance to that sold in reagents from a solution containing osmium. The present invention relates to a method for producing osmium tetroxide solution, the method comprising a step for using ozone or a similar oxidizing gas to oxidize a solution containing osmium and produce osmium tetroxide gas and a step for introducing the resulting osmium tetroxide gas into a recovery solution; the present invention further relates to a production apparatus therefor.
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