We report the effect of raw graphite size on the properties of graphite oxide and graphene prepared by thermal reduction-exfoliation of graphite oxide. Transmission electron microscope analysis shows that the lateral size of graphene becomes smaller when smaller size graphite is used. X-ray diffraction analysis confirms that graphite with smaller size is more effectively oxidized, resulting in a more effective subsequent exfoliation of the obtained graphite oxide toward graphene. X-ray photoelectron spectroscopy demonstrates that reduction of the graphite oxide derived from smaller size graphite into graphene is more efficient. However, Raman analysis suggests that the average size of the in-plane sp(2)-carbon domains on graphene is smaller when smaller size graphite is used. The enhanced reduction degree and the reduced size of sp(2)-carbon domains contribute contradictively to the electrical conductivity of graphene when the particle size of raw graphite reduces. (C) 2015 Elsevier Ltd. All rights reserved.