A seismic ACROSS transmitter installed at Tono mine was used to detect the temporal variation of transfer function. The sequence of transfer functions thus obtained for one year is further stacked in a way of weighted moving average of 30 days to give a smoothed sequence of transfer functions with larger S/N under the expense of time resolution of temporal variation. The transfer function sequence shows definitely the presence of temporal variation at around the P and S wave arrivals surely beyond the uncertainty level specified by S/N.