Surface-enhanced Raman scattering (SERS) greatly improves molecule sensitivity compared with ordinary Raman spectroscopy. To excite and detect SERS efficiently, we fabricated glass-made microcapillary tubes decorated with silver nanoparticles inside them. The capillary tubes work as sample containers, where the required sample volume is in the order of a few nanoliters. The capillary tubes also play the role of optical waveguides. The tubes guide the excitation laser light through them so that the light illuminates whole silver nanoparticles inside the tubes at once. The tubes guide the SERS light to the tube end efficiently. The decoration of silver nanoparticles inside the tubes was performed by the silver mirror reaction. By making the tubes thinner and longer, highly sensitive SERS spectroscopy can be achieved. Our method would be a powerful tool for high-sensitivity molecule detection where the sample volume and concentration are extremely low.