1. A command recognition device comprising: an utterance understanding unit that determines or selects word sequence information from speech information; speech confidence degree calculating unit that calculates degree of speech confidence based on the speech information and the word sequence information; a phrase confidence degree calculating unit that calculates a degree of phrase confidence based on image information and phrase information included in the word sequence information; an image analysis unit that calculates a trajectory-of-motion of an object from the image information, wherein the trajectory of motion is calculated based on time-series data of position coordinates of a trajectory in a motion of an object, where the position coordinates are variable in time; and a motion control instructing unit that determines whether a command of the word sequence information is to be executed based on a command estimation value which is calculated using the degree of speech confidence and the degree of phrase confidence, wherein the phrase confidence degree calculating unit calculates a degree of motion confidence representing the confidence that the trajectory-of-motion comprises a motion of the phrase information as the degree of phrase confidence.