A silicon nitride polishing liquid for chemical mechanical polishing of a body to be polished in a planarization process for manufacturing of a semiconductor integrated circuit, the body to be polished including at least a first layer containing silicon nitride and a second layer containing at least one silicon-including material selected from the group consisting of polysilicon, modified polysilicon, silicon oxide, silicon carbide, and silicon oxycarbide, the silicon nitride polishing liquid having a pH of 2.5 to 5.0, and including (a) colloidal silica, (b) an organic acid that has at least one sulfonic acid group or phosphonic acid group in the molecular structure thereof and functions as a polishing accelerator for silicon nitride, and (c) water.