Two-phase flow patterns in a mini-hydrocyclone with different insertion depths of the vortex finder were measured by a phase Doppler particle analyzer. The distributions of velocity, concentration, root-mean-square velocity, and average diameter of particles were evaluated. A deeper insertion of the vortex finder led to smaller tangential velocity at the cross section near the column cone interface. When the vortex finder insertion depth did not reach the column cone interface, the vortex finder was inserted deeper and the line of zero velocity value migrated more distinctly inward. When the vortex finder insertion depth reached or exceeded the column cone interface, strong turbulence occurred near the vortex finder. The distributions of the axial velocities of particles and root-mean-square velocities indicated that circulation flow existed at the bottom part of the mini-hydrocyclone.