Titanium and its alloys have high specific strength, excellent corrosion resistance, and good biocompatibility. By those good properties, they are applied to wide fields, airplanes to sports goods. However, their fields are not expanded, because they are expensive. To reduce the cost, Ti-Mn system beta type alloys were developed. In those alloys, valuable metallic elements are not used as alloying elements. However, though Ti-Mn system beta type alloys have high hardness and high 0.2% proof strength, the resistance of deformation is higher due to them. To decrease deformation resistance, development of Ti-Mn-V-Al alloy by partial substitution of V with Mn was studied. In solution treated and quenched state, those alloy had only beta phase and equaxied grain. Vickers hardness decreased with replacement of Mn by V. Aging behavior will be explained in detail at the meeting.