The present invention provides an apparatus for measuring the amount of fuel that detects an interface between air and fuel without using a contact and a float in order to measuring the amount of fuel in a fuel tank. The apparatus for measuring the amount of fuel includes a step pole plate unit, an oscillator unit, a rectifier circuit, a comparator circuit, and a CPU. The step pole plate unit includes pairs of first and second plates and a plurality of steps for detecting dielectric constants of materials between the first and second plates. The oscillator unit generates frequencies corresponding to the dielectric constants detected by the plurality of steps. The rectifier circuit or an F-V circuit converts the frequencies output from the oscillator unit into DC voltages corresponding to the frequencies. The comparator circuit compares the DC voltages output from the rectifier circuit or the F-V circuit with a reference voltage, and outputs signals corresponding to results of the comparison between the DC voltages and the reference voltage. The CPU detects a position of an interface between air and fuel on the basis of the signals output from the comparator circuit, and outputs the amount of fuel corresponding to the position of the interface between air and fuel.