An object of the present invention is to provide a method for removing even small viruses from a high concentration monoclonal antibody solution using a membrane, and thus for recovering the antibody within a short time at high yield in the form of a filtrate. The present invention provides a method for producing a preparation containing a monoclonal antibody, which comprises a step of removing viruses by filtering viruses in a monoclonal antibody solution using a virus-removing membrane, wherein (1) the monomer content of the monoclonal antibody accounts for 90% or more； (2) the monoclonal antibody concentration in the monoclonal antibody solution ranges from 20 mg/ml to 100 mg/ml； (3) the monoclonal antibody solution contains at least a basic amino acid； and (4) the parvovirus removal rate of the virus-removing membrane satisfies the following conditions: LRV (Log Reduction Value: logarithmic reduction value) ‰§ 4.
