PURPOSE: To provide a core for a coaxial cable with which at least one property among various electric properties such as electrostatic capacity, characteristic impedance, and transmission delay time, etc., can be uniformalized, provide a coaxial cable using the core, and provide a manufacturing method of the core.

CONSTITUTION: A core 9 for a coaxial cable is one consisting of a first dielectric layer 2 on the outer circumference of a conductor and a second dielectric layer 3 (a skin layer), and a cable using the core and a manufacturing method of the core are provided. A computing apparatus 7 computes the difference of the electrostatic capacity value for every unit length, which is previously set, of the core 9 from the electrostatic capacity value measured by an electrostatic capacity measuring apparatus 6 for every unit length when the difference is produced. Based on the result, a control apparatus 8 controls an extruding apparatus 4 so as to adjust the thickness of the dielectric layer 3.