1. An apparatus for measuring a blood pressure of a subject susceptible to noise during measurement, comprising: a cuff configured to be placed around the subject's arm containing an artery; an inflating unit, coupled to the cuff, for inflating the cuff; a pressure transducer coupled to the cuff; and a controlling/processing unit, coupled to the cuff, the inflating unit and the pressure transducer, respectively, for controlling the inflating unit to inflate the cuff to an initial inflation pressure, controlling the cuff to be deflated from the initial inflation pressure, obtaining a cuff pressure signal and a sequence of raw oscillometric pulse amplitudes (raw OA) relating to counter-pressure of the artery from the pressure transducer as the cuff is deflated from the initial inflation pressure, calculating a respective weight ω for each of the raw oscillometric pulse amplitudes, the respective weight ω being indicative of level of noise corresponding to the raw oscillometric pulse amplitude and being obtained based on variation rate of oscillometric pulse amplitudes neighboring to each raw oscillometric pulse amplitude, modifying each of the raw oscillometric pulse amplitudes based on the respective weight ω to obtain a sequence of current oscillometric pulse amplitudes (current OA) replacing the raw oscillometric pulse amplitudes, defining a maximum oscillometric pulse amplitude among the current oscillometric pulse amplitudes, determining a systolic pressure relating to the blood pressure of the subject based on the maximum oscillometric pulse amplitude, the cuff pressure signal and a first ratio, and determining a diastolic pressure relating to the blood pressure of the subject based on the maximum oscillometric pulse amplitude, the cuff pressure signal and a second ratio, wherein the controlling/processing unit modifies each of the raw oscillometric pulse amplitudes (raw OA) by the steps of: utilizing the raw oscillometric pulse amplitudes neighboring said one raw oscillometric pulse amplitude (OA) having respective weights higher than a threshold value to calculate a respective target oscillometric pulse amplitude (target OA) in a curve-fitting way; and calculating the current oscillometric pulse amplitude (current OA) by the following formula: 
 current OA =ω×raw OA +(1−ω)×target OA.