This work describes catalytic aqueous-phase oxidation of furfural to maleic acid. The heterogeneous Cu-phosphate catalysts were prepared by coprecipitation method at different atomic ratios of precursors and characterized by various techniques. The CaCu-phosphate catalyst showed the best catalytic performance. Using this catalyst under reaction conditions (115 A degrees C and 0.8 MPa of O-2) 37.3 mol% yield and 54.8% selectivity of maleic acid were achieved. This catalyst can be recycled more than four times producing practically the same selectivity as fresh one by 13% decrease in furfural conversion. The proposed mechanism involves furoic acid as an intermediate in the formation of maleic acid.