Disclosures of the present invention describe a current sensing device and method, wherein the current sensing device comprises: at least one magnetic sensor, a signal receiving unit and a microprocessor. Particularly, the present invention provides an environmental magnetic field filtering unit and an effective current calculation unit in the microprocessor, such that the microprocessor is able to calculate the value of a current flowing in a specific electrical cable with high accuracy based on a sensing magnetic field outputted from the magnetic sensor.