A blood pressure measurement apparatus (1; 1A; 1B; 1C; 1D; 1E; 1F) comprising: blood pressure measurement means adapted to measure a subject's blood pressure; physiological information measurement means (6, 13, 14) adapted to measure physiological information which is blood oxygen saturation level; physiological information storage means adapted to store a series of values of said physiological information in level as measured by said physiological information measurement means (6, 13, 14) for a predetermined period of time, said physiological information storage means being adapted to intermittently or continuously store said values of said physiological information in level as measured for said predetermined period of time; and determination means (7, 15) adapted to determine whether a value of said physiological information as currently measured by said physiological information measurement means (6, 13, 14) for determination of initiation of measurement of said subject's blood pressure exceeds a threshold value, wherein said blood pressure measurement means is adapted to, when said determination means determines that the value of said physiological information as currently measured exceeds the threshold value, be initiated to measure said subject's blood pressure, wherein: said determination means (7, 15) includes calculation means adapted to calculate an average value and a standard deviation of measured values of said series of physiological information previously stored; and when said physiological information currently measured for determination of initiation of said blood pressure measurement provides a value exceeding said threshold value obtained from said average value and said standard deviation calculated by said calculation means, said determination means (7, 15) is adapted to determine that the provided value exceeds the threshold value and said blood pressure measurement means is initiated. blood pressure measurement means adapted to measure a subject's blood pressure; physiological information measurement means (6, 13, 14) adapted to measure physiological information which is blood oxygen saturation level; physiological information storage means adapted to store a series of values of said physiological information in level as measured by said physiological information measurement means (6, 13, 14) for a predetermined period of time, said physiological information storage means being adapted to intermittently or continuously store said values of said physiological information in level as measured for said predetermined period of time; and determination means (7, 15) adapted to determine whether a value of said physiological information as currently measured by said physiological information measurement means (6, 13, 14) for determination of initiation of measurement of said subject's blood pressure exceeds a threshold value, wherein said blood pressure measurement means is adapted to, when said determination means determines that the value of said physiological information as currently measured exceeds the threshold value, be initiated to measure said subject's blood pressure, wherein: said determination means (7, 15) includes calculation means adapted to calculate an average value and a standard deviation of measured values of said series of physiological information previously stored; and when said physiological information currently measured for determination of initiation of said blood pressure measurement provides a value exceeding said threshold value obtained from said average value and said standard deviation calculated by said calculation means, said determination means (7, 15) is adapted to determine that the provided value exceeds the threshold value and said blood pressure measurement means is initiated. said determination means (7, 15) includes calculation means adapted to calculate an average value and a standard deviation of measured values of said series of physiological information previously stored; and when said physiological information currently measured for determination of initiation of said blood pressure measurement provides a value exceeding said threshold value obtained from said average value and said standard deviation calculated by said calculation means, said determination means (7, 15) is adapted to determine that the provided value exceeds the threshold value and said blood pressure measurement means is initiated.