There are provided a subject information processing apparatus suitable for acquiring a moving image by consecutively receiving acoustic waves from an observation target subject region and an image display method. First combined image data is generated by combining at least two of i-th image data to (i+m)-th image data (i+m<；N, where i and m are natural numbers) out of N pieces of image data based on electrical signals acquired when a probe detects the acoustic waves respectively at N positions (N is 3 or a larger integer) at different relative positions to the subject. Second combined image data is generated by combining at least two of an (i+n)-th to an (i+n+m)-th image data (n is a natural number). An image based on the first combined image data is updated to an image based on the second combined image data.
