Static leaching tests of simulated nuclear waste glass were carried out at 90$^{\circ}$C in an air atmosphere using a MgCl$_{2}$ solution and deionized water. As a result, in the MgCl$_{2}$ solution, temporal plateau and following resumption of glass dissolution were observed, while an ordinary dissolution behavior, which shows rate decrease with time, was observed in the deionized water. It is considered that these unique dissolution behavior in MgCl$_{2}$ solution may be related to the evolution of the Mg-containing mineral species deposited on the glass surface.