We report the development of an ultrahigh-Q aluminum superconducting microwave resonator on diamond. Our lumped-element LC resonator consists of a central inductive wire, interdigitated comb fingers and signal coupling pads. The resonance frequency of the ground-state mode is measured to be 2.80 GHz with a maximum internal quality factor of 1.0 x 10(6) at 20 mK. Replacing the micron-scale inductive wire with a nanometric one, our resonator will make it possible to detect and manipulate single solid-state qubits, e.g. nitrogen-vacancy centers, using single microwave photons. (C) 2019 The Japan Society of Applied Physics