In the present proposal, we would like to investigate beta-Li2IrO3, a 5d based hyper-honeycomb system, where strong Kitaev-type anisotropy of magnetic couplings triggers a peculiar non-coplanar magnetic order below 38 K. Bulk measurements suggest that external magnetic field tends to suppress this ordered state, and a new state lacking any clear signatures of long-range order, presumably a quantum spin liquid state, is formed above 3 T. Since until date no microscopic measurements have been done to unveil the nature of this field-induced state, µSR would be one of the best technique to employ. We propose µSR measurements on beta-Li2IrO3 at zero field and in applied fields, where the new magnetic state is formed. µSR will provide indispensable information on the nature of this field-induced state.