Understanding nanoscale fluid flows is fundamental issue in chromatography. Recently, our group has reported unique liquid properties in extended nanospace (10-1000 nm), and suggested a liquid model with loosely coupled water molecules within 50 nm of fused-silica surface. The unique water properties may affect fluid flows, however, measurement of flow profile in nanochannels has been difficult because of the space size smaller than light wavelength. In this study, we investigated pressure driven flows in extended nanochannel by developing evanescent wave-based particle tracking velocimetry. 64 nm fluorescent particles were used as tracer and injected into a nanochannel of 410 nm depth and 50 μm width. The particles flowing through the channel were illuminated by the evanescent wave generated with total internal reflection of the laser beam at the channel wall. Based on the exponential decay of the evanescent wave from the wall, the depth-wise position of nanoparticles in the nanochannel was determined from the fluorescent intensity. In order to make measurement error by significant Brownian diffusion of the nanoparticle negligible, a measurement system of time resolution of 260 ms was developed to decrease the diffusion displacement to 62 nm, which is similar to the particle size. From the time sequence images, distribution of particle velocity in the nanochannel was successfully obtained. The results indicated parabolic flow profiles with similar velocity magnitude to theoretical calculation based on Hagen-Poiseuille equation. However, the flow profiles suggested slip velocities even in the hydrophilic fused-silica nanochannel. The developed method will provide important knowledge of nanoscale fluid dynamics, which is a basic science in chromatography and nanofluidic devices.