A SnO₂ ISFET device and manufacturing method thereof. The present invention prepares SnO₂ as the detection membrane of an ISFET by sol-gel technology to obtain a SnO₂ ISFET. The present invention also measures the current-voltage curve for different pH and temperatures by a current measuring system. The temperature parameter of the SnO₂ ISFET is calculated according to the relationship between the current-voltage curve and temperature. In addition, the drift rate of the SnO₂ ISFET for different pH and hysteresis width of the SnO₂ ISFET for different pH loop are calculated by a constant voltage/current circuit and a voltage-time recorder to measure the gate voltage of the SnO₂ ISFET.