An ultrasonic sensing apparatus held next to a target can detect vital signs of the target. The ultrasonic sensing apparatus includes a first flexible circuit board, a transmitting layer, a readout layer, and a receiving layer. Emitting elements in the transmitting layer generate ultrasonic signals and the receiving layer receives reflected ultrasonic signals and converts the reflections into electrical signals. The emitting elements are staggered in relation to elements of the receiving layer for better resolution and accuracy. The readout layer reads the electric signals for calculating vital signs. The readout layer includes input lines and output lines and readout pixels are defined by the crossing points of input and output lines. Ultrasonic signals are generated during a first period, and the reflections are read in a second period next following. The readout layer completes one reading operation corresponding to one readout pixel during the second period.
