A method of analyzing a sample solution comprises the steps of allowing the sample solution to drip onto a sample retaining means, depositing a solute of the sample solution by evaporating a solvent thereof, irradiating infrared radiation onto this solute, and measuring the intensity of the infrared radiation which is reflected by the solute and the sample retaining means disposed under the solute so as to obtained an infrared spectrum. An apparatus for preparing a sample solution is provided for carrying out the above-described method. In this apparatus, the sample retaining means is moved so that a layer of solute which corresponds to each droplet of sample solution is continuously formed on the sample retaining means.