The present invention provides a means to ensure a further increase in the therapeutic effects provided by enzyme replacement therapy against lysosomal disease. The present invention is directed to a recombinant human saposin B protein containing phosphorylated carbohydrate chains, a lysosomal enzyme activator comprising such a recombinant protein, and a pharmaceutical composition for treatment of lysosomal disease, which comprises such a recombinant protein and a lysosomal enzyme, etc.