A shell plate sound isolating structure is applied in a fan (100), and includes a hollow plate body (1) having a front plate (11), a rear plate (12) and an annular peripheral plate (13), wherein the rear plate (12) has a first wind port (14) where the fan (100) is disposed, the front plate (11) or the annular peripheral plate (13) has at least one second wind port (15); and at least one partition plate (2), disposed inside the hollow plate body (1) and capable of fully blocking between the first wind port (14) and the at least one second wind port (15), wherein a partition space (s) is formed between the at least one partition plate (2) and the hollow plate body (1) for forming an elongated flow channel (f) allowing the first wind port (14) and the second wind port (15) to be in communication.