A signal amplifying circuit with noise suppression function includes a first circuit module and a second circuit module. The first circuit module includes a current source and a switch. The current source is connected to an input stage for inputting a current. The switch is connected to a first output terminal and adapted to switch the input stage and the first output terminal according to a chopping frequency. The second circuit module includes an equivalent capacitance disposed between an output stage and a second input terminal connected to the first output terminal. The signal amplifying circuit controls current volume of the current source and capacity value of the equivalent capacitance to accordingly adjust an interior frequency bandwidth of the signal amplifying circuit, and the interior frequency bandwidth is smaller than the chopping frequency and greater than an input signal of the input stage.