Magnetic fields affect star formation on a broad range of scales, from parsec to hundreds au scales. In this talk, I will present our recent studies on magnetic fields in star forming regions and young stellar objects (YSOs) on intermediate (1000-10000 au) and small (~100 au) scales. For the intermediate-scale magnetic fields, I will introduce the B-fields In STar forming Region Observations (BISTRO) project, which is a large program of the James Clerk Maxwell Telescope, focusing on the results toward the Serpens Main molecular cloud. Particularly, orientations of magnetic fields with respect to structures will be discussed. For the small scales, I will discuss the effects of magnetic fields on early disk formation. Previously, when magnetic fields are aligned to the bipolar outflow of a YSO, it is not expected to form a disk at the early stage, due to catastrophic magnetic braking. However, our recent ALMA observations toward L1448 IRS 2, which has a rotation detected and its magnetic fields aligned to the bipolar outflow (poloidal fields) on ~1000 au scales, show that the fields switch to toroidal at the center on ~100 au scales. This result suggests that magnetic braking may not be so catastrophic for early disk formation even in YSOs with magnetic fields aligned to the bipolar outflow.