Abstract: In order to increase durability against repeated flexure caused in a body tissue or flexure having a very small radius of curvature, and to reduce mechanical stress applied by a lead body on the body tissue, a lead body (20) of an implantable electrode lead is constituted by a conductive coil (24) and a sheath (22). The conductive coil (24) is obtained by helically winding a conductive wire (26), formed with an insulating coating layer (28) and having a diameter (d), to have a coil pitch diameter (mean diameter) (D). The sheath (22) is made of an electrical insulating material. An outer diameter G of the lead body (20) is set to 2 mm or less. The sheath (22) is formed of a soft material having a Shore hardness of 80A or less. The conductive coil (24) is set to have a spring index (D/d) of 7.8 or more.