A high side current monitoring apparatus monitors a load current flowing into a load apparatus. The high side current monitoring apparatus includes a current mirror unit, an active high voltage unit, a voltage detection unit and a bias unit. The current mirror unit generates a mirrored current and outputs the mirrored current according to the load current. The active high voltage unit is electrically connected to the current mirror unit and receives the mirrored current and works in a linear area to withstand a high voltage. The voltage detection unit is electrically connected to the active high voltage unit and detects a voltage drop across the voltage detection unit and caused by the mirrored current. The bias unit is electrically connected to the active high voltage unit and provides the active high voltage unit with a bias.