To provide a circuit board which has improved production yield and can stably operate, and to provide an electronic apparatus.

The circuit board includes: a dielectric substrate 1 having a first recess 1a to be a coolant flow passage, on one principal plane; and a first metal plate 2 provided on the one principal plane of the dielectric substrate so as to cover the first recess. Preferably, the circuit board further includes a second metal plate 3 provided on the other principal plane of the dielectric substrate. It is preferable that the first metal plate includes a mounting portion on which an electronic element 4 is to be mounted, and a circuit portion electrically connected to the electronic element. It is preferable that the dielectric substrate has a projection or a second recess between the mounting portion and the circuit portion.