By using a heterobimetallic catalyst, (CO)(4)(PEtPh2)-W(mu-PPh2)Rh(CO)(PPh3), chemoselective hydroformylation of monosubstituted alkenes proceeds efficiently at room temperature under atmospheric pressure of CO/H-2, without affecting functional groups such as disubstituted alkene moieties, aryl and alkenyl iodide moieties, and hydroxy and carboxy groups.