The phase constitution, lattice parameter, martensitic and magnetic transformation behavior and hardness of the Ni2MnGa-Cu2MnAl pseudobinary alloys designed as (Ni2MnGa)x(Cu2MnAl)1-x were investigated in order to improve magnetic properties of Ni2MnGa. It was revealed that L21 Ni2MnGa and Cu2MnAl make a continuous solid solution of (Ni,Cu)2Mn(Ga,Al) when heat treated at 1073K, and that the lattice parameter of the L21 phase increases monotonously with increasing the compositional ratio x, that is, the amount of Cu2MnAl. Curie temperature TC also increases with increasing x. On the other hand, the martensitic transformation temperature of Ni2MnGa seems to decrease rapidly by adding Cu2MnAl. Hardness of the alloys heat-treated at 1073K ranges from HV200 to HV370, and solution hardening was recognized by mixing. When heat treated at 773K, a phase decomposition from L21 phase to Cu9Al4 and b-Mn was confirmed in the Cu2MnAl-rich alloys. The phase decomposition causes a decrease in the lattice parameter of L21 phase and TC and a significant increase in hardness.