A process for the production of an aluminum-diamond composite, characterized by comprising the step of preparing a diamond powder having a specific diameter, the step of adding a colloidal silica to the diamond powder to form a slurry, the step of subjecting the slurry to press forming or slip casting to produce a compact of the diamond particles, the step of firing the compact either in air or in a nitrogen atmosphere to form a porous diamond preform, the step of heating the porous diamond preform, the step of heating an aluminum alloy to a temperature equal to or above the melting point of the alloy and impregnating the molten alloy into the porous diamond preform to make a flat plate-like aluminum-diamond composite wherein both surfaces are covered with surface layers containing an aluminum-base metal, and the step of working the aluminum-diamond composite into an aluminum-diamond composite.