We microscopically investigate chiral magnetic orders in the absence and presence of magnetic field in a chiral magnetic crystal CrNb3S6 by means of low-temperature Lorenz transmission electron microscopy and small-angle electron scattering method. Based on detailed analyses in both real and reciprocal space, we directly observe that chiral soliton lattice (CSL) emerges in small magnetic fields applied perpendicular to the chiral crystallographic axis. CSL develops from chiral helimagnetic structure (CHM) with increasing the spatial period from 48 nm toward sample size in rising magnetic fields. Chiral magnetic orders of CSL and CHM do not exhibit any structural dislocation, indicating their high stability and robustness. This is because chiral magnetic orders are macroscopically induced by monoaxial Dzyaloshinkii-Moriya exchange interaction that is allowed in hexagonal CrNb3S6 crystals belonging to noncentrosymmetric chiral space group. Present observations of periodic, nonlinear, tunable, and robust CSL will be the first step to explore fascinating functions of CSL for magnetic and spintronic device applications using chiral magnets.