In order to overcome the difficulties of conventional methods for measuring concentration of solid-phase in the solid-liquid two-phase flow in micro-devices, a unique measuring technique using electromagnetic induction with diluted magnetic fluid is applied to measure the solid-liquid two-phase flow in a micro-tube. In this method, 5 wt.% magnetic fluid diluted by distilled water was used. In order to verify the validity of the technique for measuring solid-liquid two-phase flow, experiments in actual solid-liquid two-phase flow with particle drop flow were performed. The present method has demonstrated a promising way of measuring the particles diameter with satisfactory accuracy.