Infrared spectra of the OH stretching vibrations of the jet-cooled salicylic acid (SA) monomer and dimer were measured for both their electronic ground (S₀) and first excited (S₁) states. For the SA monomer, conformations of two rotational isomers (rotamers) which have been identified by the electronic transitions were determined based on the infrared spectra with a help of theoretical calculations. The intramolecular hydrogen-bonded OH stretching vibrations of the monomer showed a drastic change upon the electronic excitation, and it was consistent with the distortion of the H-chelate ring in the S₁ state predicted by theoretical calculations of Sobolewski and Domcke (Chem. Phys. 232 (1998) 257). Structures of the dimer in the S₀ and S₁ states were also determined by the observation of the OH stretching vibrations. No evidence was found for intermolecular double proton transfer both in the S₀ and S₁ states of the dimer.