Provided are a blood pressure estimation apparatus, a sphygmomanometer, a blood pressure estimation system, and a blood pressure estimation method which allow continuous blood pressure measurement without adding stress to a subject's body. A plurality of sensors and a controller are included. The plurality of sensors each detect a pulse wave of a subject without applying, to the subject, pressure that is greater than predetermined pressure, and the controller calculates an estimated value of subject's blood pressure continuously, based on a measured value of the subject's blood pressure acquired from a sphygmomanometer and on output of the sensors.
