In a gas turbine blade where a part of the γ′ phase precipitation strengthened type Ni-based alloy base material is composed of a weld metal, the weld metal is a Ni-based alloy containing Ta from 4.8 to 5.3 wt. %, Cr from 18 to 23 wt. %, Co from 12 to 17 wt. %, W from 14 to 18 wt. %, C from 0.03 to 0.1 wt. %, Mo from 1 to 2 wt. %, and Al of 1 wt. % or less, in which the oxygen content is 0 to 30 ppm, the Ti content from 0 to 0.1 wt. %, and the Re content from 0 to 0.5 wt. %. A blade base metal is manufactured by the step of stripping, the step of solution heat treatment where the γ′ phase is dissolved again, the step of welding in an inert gas chamber by a TIG method using a welding wire where the weld metal can be obtained, the step of HIP treatment at 1100° C. to 1150° C., and the step of an aging treatment at 835° C. to 855° C.