A wireless device in a first communication system configured to use a first band and a third band different from the first band, comprising: a communication interface configured to perform communication by using the first band and the third band; a first monitoring interface configured to monitor a situation of use of a second band for use by the communication interface and different from the first band and the third band, the second band being used in a second communication system different from the first communication system that is configured to use the first band and the third band; and a second monitoring interface configured to monitor a situation of use of the third band and the first band, the third band being monitored when the first band is used by the communication interface; a controller configured to, when the situation of use monitored by the first monitoring interface changes from non-use to use, cause the communication interface to change from using the first band to using the third band based on the situation of use of the third band as monitored by the second monitoring interface, a first filter provided between the communication interface and an antenna the first filter configured to pass a signal in the first band; and a second filter provided to branch from a node between the first filter and the antenna, the second filter having a bandwidth narrower than that of the first filter, and configured to pass a signal in a portion of the first band toward the second band, wherein the first monitoring interface is configured to monitor the situation of use of the second band based on an output from the second filter by using a leak component of a signal in the second band. a communication interface configured to perform communication by using the first band and the third band; a first monitoring interface configured to monitor a situation of use of a second band for use by the communication interface and different from the first band and the third band, the second band being used in a second communication system different from the first communication system that is configured to use the first band and the third band; and a second monitoring interface configured to monitor a situation of use of the third band and the first band, the third band being monitored when the first band is used by the communication interface; a controller configured to, when the situation of use monitored by the first monitoring interface changes from non-use to use, cause the communication interface to change from using the first band to using the third band based on the situation of use of the third band as monitored by the second monitoring interface, a first filter provided between the communication interface and an antenna the first filter configured to pass a signal in the first band; and a second filter provided to branch from a node between the first filter and the antenna, the second filter having a bandwidth narrower than that of the first filter, and configured to pass a signal in a portion of the first band toward the second band, wherein the first monitoring interface is configured to monitor the situation of use of the second band based on an output from the second filter by using a leak component of a signal in the second band.