To provide a commercially advantageous manufacturing method of an alkoxysilane that is reduced in the amount of by-products, without using a halogenated silane as a raw material and a large amount of a compound containing titanium and the like.

Polysiloxane and an organic hydroxy compound are caused to react in the presence of a Lewis acidic metal alkoxide having, as a central metal, a metal that gives a frequency of a metal-chlorine bond of at most 390 cm-1 in the state of a metal chloride.