A new neutron focusing device with bent Si-single crystal has been installed at high-resolution neutron diffractometer dedicated to strain/stress investigations in polycrystalline materials and introduced into routine operation as a neutron strain scanner using reactor neutrons from supermirror guider at Kyoto University Research Reactor (KUR). Properties of the diffractometer are described on the basis of experimental results when one slab or two slabs of curved Si single crystals are employed as monochromator : i.e. 1) the luminosity 2) the absolute value of monochromatic neutrons with the Au-foil activation method, 3) beam profiles with the imaging plate method, 4) characterization of the diffractometer with alpha Fe (211) peak and its comparison with the Bragg optical prediction. It is confirmed that the FWHM of the instrumental delta d/d-profile of the peak can be less than 3 x 10(-3) at d = 1.17 A and the resolution permits us to investigate both the macro- and microstrains with good luminosity. The luminosity becomes about ten times comparing with the one by the conventional pyrolitic graphite monochromator (PG).