An electrochemical glucose sensor based on a screen-printed diamond electrode was fabricated as a low-cost, disposable, and sensitive electrode. Amperometric detection of glucose was achieved by using a glucose-oxidase-immobilized cobalt phthalocyanine/boron-doped diamond powder (GOx-CoPc/BDDP)-printed electrode, with a linear calibration curve in the concentration range of 0.2-1.0 mM. The background current for the GOx-CoPc/BDDP-printed electrode stabilized faster than that for the GOx-CoPc/carbon-printed electrode, which confirms its practical usefulness for the detection of glucose at low concentrations.