In this letter the scaling properties of the period-adding sequences i
n a so-called ''multiple Devil's staircase'' are reported. It is certi
fied both analytically and numerically that the width of the i-th phas
e-locked plateau in a sequence scales as In \Delta e(i)\ proportional
to i, and the position of the plateau scales as In \e(infinity) - e(i)
proportional to i. These properties are qualitatively different fi om
those of the period-adding sequences in conventional Devil's staircas
es.