Measurement of velocity profiles along a laminar boundary layer in a streamwise corner was carried out by using particle image velocimetry in contrast to conventional hot-wire anemometry. To make the measurement successful, the laser light source for particle image velocimetry was placed at a far-downstream station, and a light sheet was emitted in parallel to the corner intersection line. The plate was tilted at very small angles relative to the freestream to realize the laminar flow starting from the corner leading edge. Discussions on the characteristic features of the velocity profile in the bisector plane are given based on the measurement data. It was found that the measured velocity profiles correspond to the Blasius branch solution of the theoretical corner layer equations.