To provide a high frequency circuit board which includes an insulating layer (LCP substrate) which is excellent in solder thermal resistance, while sufficiently maintaining the characteristics of liquid crystal polyester, such as dielectric characteristics or the like.

The high frequency circuit board includes an insulating layer consisting of: a sheet (A) which is made of inorganic fiber and/or carbon fiber; and liquid crystal polyester (B) which is solvent-soluble and whose flow beginning temperature is 250C. Preferably, the liquid crystal polyester (B) has a structural unit derived from aromatic amine which has phenolic hydroxy group, and the sheet (A) is a glass cloth.