A mobile phone with fat measuring function including a mobile phone control module, a display device, a fat measuring control circuit, a constant current electrode pair and a voltage measuring electrode pair is provided. Both the display device and the fat measuring control circuit are coupled to the mobile phone control module, while both constant current electrode pair and voltage measuring electrode pair are coupled to the fat measuring control circuit. When the user touches the constant current electrode pair and the voltage measuring electrode pair, the fat measuring control circuit firstly applies a predetermined current to the constant current electrode pair. The predetermined current causes the voltage measuring electrode pair to generate a measured voltage. The user's body fat percentage is then generated according to the measured voltage and the user's weight data, and the body fat percentage is displayed on the display device.