Effects of one-dimensional periodic staircases on minigaps are theoretically investigated. Various cases are classified according to the step height. Observed positions of minigaps can be explained by a staircase model whose step height is half a lattice constant. In this case (i) the minigaps are assigned from the lowest as ${E}_{0}$, ${E}_{1}$, ${A}_{1}$, ${E}_{\ensuremath{-}1}$, ${E}_{2}$, ${A}_{2}$, ${E}_{\ensuremath{-}2}$, and so on, where ${E}_{r}$ stands for an intervalley minigap and ${A}_{r}$ for an intravalley one; (ii) ${E}_{r}$ observed in dc conduction are approximately given by ${E}_{r}\ensuremath{\approx}23(\frac{\ensuremath{\theta}}{\ensuremath{\alpha}})\mathrm{exp}[\ensuremath{-}(\frac{1}{4}){r}^{2}{W}^{2}]sin(2\ensuremath{\varphi}){N}_{\mathrm{eff}}$ (meV) for $|r|\ensuremath{\pi}\ensuremath{\alpha}\ensuremath{\theta}l1$, where $\ensuremath{\theta}$ and $\ensuremath{\varphi}$ are polar and azimuthal angles of tilting, $\ensuremath{\alpha}$ is a parameter expressing a step structure and of the order of one, $W$ is a parameter specifying the disorder of staircase, and ${N}_{\mathrm{eff}}=\frac{({N}_{\mathrm{inv}}+3{N}_{\mathrm{depl}})}{{10}^{12}}$ ${\mathrm{cm}}^{\ensuremath{-}2}$; (iii) ${A}_{r}\ensuremath{\approx}{[{(\frac{0.46}{r})}^{2}+{83}^{2}{(\frac{\ensuremath{\theta}}{\ensuremath{\alpha}}\ensuremath{-}2{\ensuremath{\theta}}^{2})}^{2}{N}_{\mathrm{eff}}^{\frac{\ensuremath{-}2}{3}}]}^{\frac{1}{2}}\mathrm{exp}[\ensuremath{-}(\frac{1}{4}){r}^{2}{W}^{2}]{N}_{\mathrm{eff}}$ (meV); (iv) uniaxial stress along [110] or [$1\overline{1}0$] has an effect on ${E}_{r}$.