A method for manufacturing tris(β-diketonato)iridium by reacting β-diketone with an iridium compound, in which an activation treatment including (a) an alkali treatment and (b) an acid treatment described below is applied to the iridium compound to activate the iridium compound, and to subsequently react the β-diketone, (a) an alkali treatment: a treatment of adding alkali to a solution of the iridium compound to raise pH of the solution to a more alkaline side than that before the alkali addition and to not less than 10, and (b) an acid treatment: a treatment of adding acid to the solution subjected to the alkali treatment to lower pH of the solution to a more acidic side than that before the acid addition and to make the pH difference between solutions before and after the acid addition be not less than 0.1 and not more than 10. The present invention allows manufacture of tris(β-diketonato)iridium utilizing a wide variety of β-diketones.