A process for producing monosilane, which comprises disproportionating an alkoxysilane of the formula:H.sub.n Si(OR).sub.4-n (I)wherein R is an alkyl group having from 1 to 6 carbon atoms or a cycloalkyl group and n is an integer of 1, 2 or 3, in the presence of a catalyst, wherein the catalyst comprises at least one compound selected from the group consisting of aromatic alkoxides of the formula:MOAr (II)wherein M is a metal of Group Ia of the Periodic Table and Ar is a substituted or unsubstituted aromatic hydrocarbon group, and quaternary ammonium and phosphonium compounds of the formula:R.sup.1 R.sup.2 R.sup.3 R.sup.4 ZX (III)wherein each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 which may be the same or different, is a substituted or unsubstituted alkyl or aryl group, Z is a nitrogen atom or a phosphorus atom and X is an anion.