An information-processing method for calculating one of placement information regarding markers, orientation of an image-pickup means, and a parameter of the image-pickup means using captured images of markers existing in a real space, comprising the steps of: obtaining a sequence of images captured by an image-pickup means; extracting markers from the captured images; and obtaining a rough position and orientation information regarding the image-pickup means, at the time that the image pick-up means has captured each image, on the basis of the position information from the extracted markers; the method characterized by: determining, for each of a plurality of images in the sequence of captured images, whether to use a captured image of the sequence of images by: determining whether a first marker is detected in the captured image; detecting whether a second marker other than the first marker is detected in the captured image, the first marker and second marker forming a marker group; calculating a first evaluation value being an angle between vectors A and B, where A is a vector extending from the position of the image-pickup unit at the time that the image pick-up unit captured the preceding image to a representative position obtained from placement information regarding the marker group in the preceding image and B is a vector extending from the position of the image-pickup unit at the time that the image pick-up unit captured the current image to the representative position obtained from placement information in the preceding image; determining that an image is to be used if the angle is greater than a threshold; and calculating one of placement information regarding the markers, orientation of the image-pickup means, and a parameter of the image-pickup means using the captured image in the case that it is determined to use the captured image. obtaining a sequence of images captured by an image-pickup means; extracting markers from the captured images; and obtaining a rough position and orientation information regarding the image-pickup means, at the time that the image pick-up means has captured each image, on the basis of the position information from the extracted markers; determining, for each of a plurality of images in the sequence of captured images, whether to use a captured image of the sequence of images by: determining whether a first marker is detected in the captured image; detecting whether a second marker other than the first marker is detected in the captured image, the first marker and second marker forming a marker group; calculating a first evaluation value being an angle between vectors A and B, where A is a vector extending from the position of the image-pickup unit at the time that the image pick-up unit captured the preceding image to a representative position obtained from placement information regarding the marker group in the preceding image and B is a vector extending from the position of the image-pickup unit at the time that the image pick-up unit captured the current image to the representative position obtained from placement information in the preceding image; determining that an image is to be used if the angle is greater than a threshold; and calculating one of placement information regarding the markers, orientation of the image-pickup means, and a parameter of the image-pickup means using the captured image in the case that it is determined to use the captured image. determining whether a first marker is detected in the captured image; detecting whether a second marker other than the first marker is detected in the captured image, the first marker and second marker forming a marker group; calculating a first evaluation value being an angle between vectors A and B, where A is a vector extending from the position of the image-pickup unit at the time that the image pick-up unit captured the preceding image to a representative position obtained from placement information regarding the marker group in the preceding image and B is a vector extending from the position of the image-pickup unit at the time that the image pick-up unit captured the current image to the representative position obtained from placement information in the preceding image; determining that an image is to be used if the angle is greater than a threshold; and calculating one of placement information regarding the markers, orientation of the image-pickup means, and a parameter of the image-pickup means using the captured image in the case that it is determined to use the captured image.