Complex ruthenium oxides offer a variety of exotic electronic states, such as spin-triplet superconductivity, metal-insulator transition and spin-orbital ordering. We discovered a new pyrochlore ruthenate In2Ru2O7, which was found to show a magnetic transition with a sudden drop of magnetic susceptibility to nearly zero at ~220 K. While the behaviour looks similar to other ruthenates displaying a spin-singlet formation, In2Ru2O7 shows successive phase transitions accompanying a structural change, likely associated with spin and orbital degrees of freedom of Ru 4d electrons. The preliminary muSR data exclude the presence of long-range antiferromagnetic order but the nature of ground state remains elusive. We propose to perform detailed muSR study on In2Ru2O7 on ARGUS in order to disclose the magnetic ground state and spin-dynamics.