  EW Lac has shown remarkable V/R variations in 1976 - 1986, and a similar V/R
variation has started again in around 2007, after some quasi-periodic V/R
variation. For the first V/R variation event, we analyze the spectroscopic
behaviors of emission lines and shell absorption lines of the Balmer series.
The V/R variations of the H_alpha through H_delta lines are characterized by
the different manner of variations of the individual emission lines in time lag
and in duration of the V/R phases. Weak correlation is also notable between the
V/R variations and other variations of the line-profile parameter such as the
peak velocities, emission line intensities and peak separations. We analyze
shell absorption lines for higher members of the Balmer series for their
central depths and radial velocities. The optical depth of the H_alpha line is
in a range of 2000 to 6000, and its long-term variation discloses different
behaviors as compared to the V/R variations. Combining the analyses of emission
and shell absorption lines, and regarding the V/R variation as wave propagation
phenomena, we find for the 1976 - 1986 event that the V/R variation is of
retrograde structure and a spiral structure is likely formed inside the disk in
the latter half of this event. The weak correlations among physical parameters
are suggestive of the disk truncated at some radius. It is noticed that
remarkable stellar brightening has occurred in the latter half of the event,
accompanying marked decrease of emission line intensities. As for the V/R
variation appeared in around 2007, which looks like a recurrence of the
previous event, we found less developed state of the disk without appreciable
time lag.

Solar and Stellar Astrophysics