Micro-resolution Particle Image Velocimetry(Micro-PIV) was used to measure the flow in a micro-branch(Micro-Bypass). In this paper, effects of particle lump at the tip of a Micro-branch and difficulties of Micro-PIV measurements for microfluidics with branch passage were described. Micro-bypass was composed of a straight channel(200(100)${mu}$m width ${ imes}$ 80${mu}$m height) and two branches which has 100(50)${mu}$m width ${ imes}$ 80${mu}$m height. One of branches was straight and the other was curved. Experiments were performed at three regions along streamwise direction(entrance, middle and exit of branch) and five planes along vertical direction (0, ${pm}$10, ${pm}$20 ${mu}$m) for the range of Re=0.24, 1.2, 2.4. Numerical simulation was done to compare with the measurements and understand the effects of particle lump at the tip of branch. And another fluid(3% poly vinyl Alcohol aqueous solution) were adapted for this study, so there were no particle sticking. In this case, we could get velocity difference between straight and curved branches.