Noncontact atomic force microscopy (NC-AFM) images of the mixed monolayers of carboxylates prepared on a TiO₂(110)-(1×1) surface are presented. The order of the height of formate, acetate, pivalate, and propiolate molecules is reproduced in the NC-AFM images, while the difference in the height is smaller than that expected from their true heights. The shrinkage of the height difference is ascribed to the contribution of several molecules to the tip-molecule force. On the other hand, trifluoroacetate is imaged as a spot shorter than the acetate though the two ions have an equal true height. This indicates that the image contrast reflects the permanent dipole moment of the molecules. The experimental results show that the organic molecules can be individually identified by the NC-AFM and the experimentally obtained topography is interpreted referring to physical and chemical characteristics of the molecules.