A circuit device having a multilayered wiring structure and an excellent heat dissipation property, and a method of manufacturing the circuit device are provided. In a circuit device, a multilayered wiring structure including a first conductive pattern and a second conductive pattern is formed on a surface of a circuit substrate. A first insulating layer is formed entirely on the surface of the circuit substrate. The first conductive pattern and the second conductive pattern are mutually insulated by a second insulating layer. An amount and grain sizes of filler included in the second insulating layer are smaller than an amount and grain sizes of filler included in the first insulating layer. Therefore, it is easier to connect the above two conductive patterns by way of penetrating the second insulating layer.