A resistor composition comprising: a lead-free ruthenium-based electrically conductive component, a lead-free glass having a glass basicity (Po value) of 0.4 to 0.9, and an organic vehicle; wherein, MSi 2 Al 2 O 8 crystals (M: Ba and/or Sr) are present in a thick film resistor obtained by firing this composition. The ruthenium-based resistor composition is capable of forming a lead-free thick film resistor which eliminates harmful lead components from an electrically conductive component and glass, and has superior TCR characteristics, current noise characteristics, withstand voltage characteristics and stability after a heat cycling test over a wide resistance range.