An all-pass filtering module of a common mode noise suppressing device includes first and second differential transmission circuits coupled to a reference node. Each of the first and second differential transmission circuits has an input terminal and an output terminal, and includes: first and second capacitive elements coupled in series between the input terminal and the output terminal; a first inductor coupled between the input terminal and the output terminal; and a third capacitive element and a second inductor coupled in series between the reference node and a common node between the first and second capacitive elements.