A circuit board includes a substrate and at least one circuit structure. The substrate has first slots, each first slot extends along a first axis, and a length of each first slot along the first axis is greater than lengths of each first slot along other directions. The circuit structure is disposed on the substrate and includes arc segments and extending segments. Each arc segment is connected between two of the extending segments such that the circuit structure is circuitous. The circuit structure and each first slot have an interval therebetween such that each first slot and a part of a surface of the substrate are exposed by the circuit structure. Each first slot is located between adjacent two extending segments, and the first axis of each first slot passes through the corresponding arc segment. In addition, an electronic device having the circuit board is also provided.