We have deposited Mn on Pd(oon) at RT up to 30 ML. LEED pattern changed from p($1{ imes}1$) to c($2{ imes}2$) order below 0.5 ML Mn deposition. During Mn deposition, we have not found any changes in the peak position and the intensity of LEED I/V curve. Using LEED I/V curve analysis for each coverage, we found atomic structure and surface composition of c($2{ imes}2$) ordered Mn alloy on Pd(001) surface. Above 1 Ml Mn, in the first layer the Mn subplane lies above the Pd subplane by 0.32 ${AA}$. This result is very different from the earlier result of Jona et al., who contended that after annealing at 200 for 2 min, a buckled first layer with the Mn subplane lower than the Pd subplane by 0.2 ${AA}$.