The authors develop a small and simple steam-reforming reactor in a home-use size for such various heavy-hydrocarbons fuels as n-octane, n-decane, n-tetradecane and n-hexadecane in addition to n-dodecane, and measure the inside-temperature profile and the molar fractions of main gas components such as H2, CH4, CO and CO2. This reactor is designed only for laboratory-test use, not for a commercial product. As a result, the authors successfully achieve suitable inside-temperature profiles. Namely, temperature almost-linearly increases in the downstream direction along a reactor, under such two conditions as 600 950 K at the upstream end of the catalyst-layer bed in the reactor and as less-than 1,070 K everywhere in the reactor. And, the authors reveal the effects of the liquid-hourly space velocity (LHSV) upon the molar fractions, a conversion ratio and reforming efficiencies for various heavy-hydrocarbons fuels. All the molar fractions, which agree well with thermochemical-equilibrium theory, are approximately independent of LHSV. The conversion ratio is about 90 % for LHSV = 0.6 h-1, and monotonically decreases with increasing LHSV for LHSV > 0.6 h-1. Then, each reforming efficiency always attains the maximum for LHSV ≈ 0.6 h-1 being independent of fuels. This suggests the common upper limit of LHSV for practically-suitable operation.