Circuit board device and design support device

A circuit board device having a power supply region and a ground region adjacent to the power supply region, wherein, when divided into two or more power supply region by a slit, at least one region of said two or more power supply regions and the ground region that are adjacent is in the shape of has a shape that may be considered a track having a length that is larger than its width, a terminal element having an impedance that is substantially equal to a characteristic impedance between said at least one region and said ground region is connected between said power supply region and said ground region at a terminal end of said at least one region, wherein the terminal element includes a resistor and a capacitor which are series-connected, a relationship between the characteristic impedance Ze and a resistance R of the resistor satisfies (Ze/5)≦R≦(5·Ze), and a capacity C of the capacitor satisfies C≦1/(10π·fmin·Ze), where fmin is a lower limit of a radiation noise frequency of a reduction target.