Disclosed is a novel cellulase having an amino acid sequence in which the 162nd and/or 166th amino acid residues in the amino acid sequence of cellulase NCE5 are substituted. Further, a polynucleotide encoding the novel cellulase, an expression vector containing the polynucleotide, a host cell transformed with the expression vector, and a cellulase preparation and a washing composition containing the cellulase are disclosed. The cellulase of the present invention is resistant to surfactants, and maintains a high activity even under alkaline conditions.