Heunginjimun in Seoul as treasure No.1 is a wooden structure of two stories. This study investigates dynamic characteristics of Heunginjimun through ambient vibration, since it is always present by lots of traffic. Natural frequencies, damping ratios and modes are identified and compared using two strategies such as frequency domain decomposition and stochastic subspace identification techniques. Three modes in weak axis and one mode in strong axis are found. Natural frequencies turn out to have invariant values so that Heunginjimun moves as a whole body not individual bodies. Structural analysis modeling can be provided from these findings.