To provide an extruding die unit and a die member for die holding used in the extruding die unit and a die holding method capable of effectively preventing strain deformation of the die and excellent in maintainability or the like.

A concavity 23 in which a forming material is filled, is totally or partially formed around the shaft center on the inner periphery of a die holding aperture 21 in the die member 2 for die holding where the die 1 (10) is fitted. By this way, difference of thermal expansion between the die 1(10) followed by heat and the die member 2 for die holding is smaller and further, die 1 (10) pressure through the thermal expansion in the outward diameter direction is absorbed by the forming material M of the concavity 23 to effectively prevent strain deformation of the die 1 (10).