[Object] To provide a highly reliable circuit board which can be used for a long period of time and an electronic apparatus including this circuit board and an electronic component mounted thereon. [Solution] The circuit board includes a ceramic sintered body (11) and a metal wiring layer (13) provided on at least one primary surface (11a) thereof with a glass layer (12) interposed therebetween, and when the cross section of the circuit board perpendicular to the primary surface (11a) of the ceramic sintered body (11) is viewed, the ratio of the length of an interface (15) between the glass layer (12) and the metal wiring layer (13) to a length (12a) of the glass layer (12) in a direction along the primary surface (11a) is 1.25 to 1.80. As a result, good heat dissipation characteristics can be obtained, and the metal wiring layer (13) is not likely to be peeled away from the ceramic sintered body (11) due to operation of an electronic component (21) and/or cooling/heating cycles performed by repeated on-off operations thereof, so that a highly reliable circuit board which can be used for a long period of time can be provided.