1. A posture information calculation device that calculates a posture angle and position coordinates in a virtual three-dimensional space based on three-axis angular velocity information detected by three angular velocity sensors, and three-axis acceleration information detected by three acceleration sensors, the three-axis angular velocity information being information about angular velocities around three axes that are not parallel to one another, and the three-axis acceleration information being information about accelerations in three axial directions that are not parallel to one another, the posture information calculation device comprising: a sensor information acquisition section that acquires the three-axis angular velocity information, and the three-axis acceleration information; and a posture information calculation section that calculates the posture angle and the position coordinates in the virtual three-dimensional space based on the three-axis angular velocity information and the three-axis acceleration information acquired by the sensor information acquisition section, the posture information calculation section calculating a fixed coordinate system velocity vector based on an inertial coordinate system acceleration vector obtained from the three-axis acceleration information, and calculating the position coordinates in the virtual three-dimensional space corresponding to the fixed coordinate system velocity vector.