We evaluated the potential of using a compact, high-power quantum cascade laser (QCL) in the 5.7-µm wavelength range for less-invasive laser angioplasty, by observing the effects of QCL irradiation on cholesteryl oleate thin films and a porcine thoracic aorta. We compared the results obtained using QCL with those obtained using nanosecond pulsed laser by difference-frequency generation (DFG laser) at a wavelength of 5.75 µm. The QCL irradiation melted the cholesteryl oleate thin films after irradiation for 5-30 s at an average power density of 40 W/cm². On the other hand, the porcine thoracic aorta was not damaged after irradiation for 1-5 s at 40-50 W/cm². This result demonstrates that QCL selectively react with cholesteryl oleate without damaging the porcine thoracic aorta. The QCL induced more thermal damage than the DFG laser under irradiation conditions that gave comparable ablation depths. This finding demonstrates the potential of achieving less-invasive, selective treatment of atherosclerotic plaques using QCL in the 5.7-µm wavelength range, although the pulse structure of the QCL requires improvement to prevent thermal damage to a normal artery.