A user device to which frequency-hopping is to be applied, comprising: a modulation unit adapted for a system where multiple resource units are defined in a system frequency band in a frequency domain, a subframe includes a first slot and a second slot in a time domain, and each of the resource units has a length of one slot in the time domain, the modulation unit being configured to map data of the user device to resource units with different frequency bands in the first slot and the second slot; and a transmission unit (108, 110, 112, 114) configured to transmit the mapped data, wherein two or more resource unit groups each including two or more resource units that are consecutive in the frequency domain are defined in the system frequency band for each of the first slot and the second slot; the modulation unit is configured to map the data to a first resource unit in a first resource unit group in the first slot and to a second resource unit in a second resource unit group in the second slot such that the first resource unit group is apart from the second resource unit group by a bandwidth corresponding to a predetermined number of the resource unit groups; indexes are assigned to the resource units in each of the resource unit groups, the indexes gradually increasing from 1 in a direction from a low frequency side to a high frequency side; and the second resource unit in the second resource unit group to which the data are mapped in the second slot is represented by a formula: (a highest index of the resource units in the second resource unit group) + 1 - (an index of the first resource unit in the first resource unit group to which the data are mapped in the first slot). a modulation unit adapted for a system where multiple resource units are defined in a system frequency band in a frequency domain, a subframe includes a first slot and a second slot in a time domain, and each of the resource units has a length of one slot in the time domain, the modulation unit being configured to map data of the user device to resource units with different frequency bands in the first slot and the second slot; and multiple resource units are defined in a system frequency band in a frequency domain, a subframe includes a first slot and a second slot in a time domain, and each of the resource units has a length of one slot in the time domain, the modulation unit being configured to map data of the user device to resource units with different frequency bands in the first slot and the second slot; and a transmission unit (108, 110, 112, 114) configured to transmit the mapped data, wherein two or more resource unit groups each including two or more resource units that are consecutive in the frequency domain are defined in the system frequency band for each of the first slot and the second slot; the modulation unit is configured to map the data to a first resource unit in a first resource unit group in the first slot and to a second resource unit in a second resource unit group in the second slot such that the first resource unit group is apart from the second resource unit group by a bandwidth corresponding to a predetermined number of the resource unit groups; indexes are assigned to the resource units in each of the resource unit groups, the indexes gradually increasing from 1 in a direction from a low frequency side to a high frequency side; and the second resource unit in the second resource unit group to which the data are mapped in the second slot is represented by a formula: (a highest index of the resource units in the second resource unit group) + 1 - (an index of the first resource unit in the first resource unit group to which the data are mapped in the first slot). (a highest index of the resource units in the second resource unit group) + 1 - (an index of the first resource unit in the first resource unit group to which the data are mapped in the first slot).