A thick film resistor excluding a toxic lead component from a conductive component and glass and having characteristics equivalent to or superior to conventional resistors in terms of, in a wide resistance range, resistance values, TCR characteristics, current noise characteristics, withstand voltage characteristics and the like. The thick film resistor is formed of a fired product of a resistive composition, wherein the thick film resistor contains ruthenium-based conductive particles containing ruthenium dioxide and a glass component essentially free of a lead component and has a resistance value in the range of 100 Ω/□ to 10 MΩ/□ and a temperature coefficient of resistance within ±100 ppm/° C.