A cable core includes: an internal conductor; a foamed dielectric that includes a fluororesin and is formed on the internal conductor by extrusion molding; and a skin layer that covers the foamed dielectric, and is configured such that a foaming rate of the foamed dielectric is 80% or more, an average foamed cell diameter of the foamed dielectric is 10 μm or less, and a standard deviation of a foamed cell diameter of the foamed dielectric is 2.5 or less.