The invention discloses an organic Rankine cycle device and method realizing thermal energy stepped time-shared using through a single expansion machine. An organic Rankine cycle system comprises a closed loop formed by sequentially connecting a working medium pump (1), the end B of a first controller (2), a heat exchanger (3), a second controller (10), the expansion machine (13), a heat storage device (9) and the end C of the first controller (2), and a closed loop formed by sequentially connecting the outlet end of the heat exchanger (3) with a fourth controller (8), a condenser (6), a condensation circulation pump (5), a third controller (4) and the inlet end of the heat exchanger (3). An auxiliary system comprises an other-source heat removal system (11), a heat supplying system (12) and a domestic water preheating system (7). The organic Rankine cycle device can further be provided with multiple heat storage devices with different temperatures according to the requirement, so that the repeated stepped utilization of heat sources is realized; and meanwhile external medium-low-grade heat sources can be stored to avoid wasting, and the need of heat taking at any time is met.