Microtubular SOFCs with a diameter on the millimeter scale are suitable for portable power sources due to rapid start-up characteristics. The performance of conventional Ni-stabilized zirconia anodes deteriorated rapidly over a period of 3-4 h at 610 ^oC and a low steam/carbon (S/C) ratio of 0.044 in butane due to a large amount of carbon deposition. For the Ni-Gd doped ceria (Ni-GDC) anode, the electric power could be generated continuously for more than 24 h at 610 ^oC and S/C = 0.044 in butane. We manufactured and demonstrated a prototype portable SOFC system using a microtubular cell-stack. It can heat up to 400 ^oC within 2 min by burning an external LPG burner, and drive a USB device for 24 h continuously using a LPG cartridge (250 g; 3.2 kWh). This development has shown the potential of the microtubular SOFC system as portable power sources in disaster and emergency situations, for outdoor use, and for small-scale electric vehicles.