An object of the present invention is to provide a process capable of producing cycloalkanol and/or cycloalkanone with a favorable selectivity by oxidizing cycloalkane with a favorable conversion.Disclosed is a process for producing cycloalkanol and/or cycloalkanone, which comprises oxidizing cycloalkane with oxygen in the presence of mesoporous silica, wherein (1) the mesoporous silica contains at least one transition metal, and (2) a ratio of total volume of mesoporous silica particles having a particle diameter of 20 .mu.m or less to total volume of entire mesoporous silica particles is 25% or more in the mesoporous silica.