We made resistance and specific heat measurements in the spin-density-wave (SDW) state of (TMTSF)(2)AsF6 under magnetic fields. For the field direction B parallel to a and B parallel to b' we found negative magnetoresistance and its bent structure at about 1 T. At this field, we also found peak structure in the specific heat. This characteristic field appears to be independent of temperature. We found two characteristic temperatures in the temperature dependence of specific heat. They were slightly affected by the field parallel to c*-axis; less than 1 K up to 12 T. If these characteristic temperatures correspond to phase boundary, this suggests the sub-phase structure is almost field independent.