A wireless communication device (1, 2) that is arranged to receive a data packet including a packet number from another communication party (2, 1), the wireless communication device (1, 2) comprising: a storage unit (106, 213) in which the packet number is stored; a control unit (120, 220); and a wireless communication unit (101, 201) that is arranged to transmit and to receive the data packet based on control of the control unit (120, 220), wherein, after power is applied, the control unit (120, 220) is arranged to rewrite a packet number that is stored in the storage unit (106, 213), as an initial value that is determined in advance, and to check whether or not a packet number that is included in the data packet from the other communication party (2, 1) is consistent with the packet number that is stored in the storage unit (106, 213), wherein in a case where the two packet numbers are consistent with each other, the control unit (120, 220) is arranged to generate a delivery acknowledgement including the packet number that is stored in the storage unit (106, 213), to transmit the generated delivery acknowledgement from the wireless communication unit (101, 201) to the other communication party (2, 1), and to update the packet number that is stored in the storage unit (106, 213), and wherein in a case where the two packet numbers are not consistent with each other, the control unit (120, 220) is arranged to generate a disconnection instruction to which a message urging activation of a packet service is added, and to transmit the generated disconnection instruction from the wireless communication unit (101, 201) to the other communication party (2, 1), wherein the message urging activation of the packet service causes the other communication party (2, 1) to rewrite a packet number stored in a storage unit (213, 106) of the other communication party (2, 1) as the initial value. a storage unit (106, 213) in which the packet number is stored; a control unit (120, 220); and a wireless communication unit (101, 201) that is arranged to transmit and to receive the data packet based on control of the control unit (120, 220), wherein, after power is applied, the control unit (120, 220) is arranged to rewrite a packet number that is stored in the storage unit (106, 213), as an initial value that is determined in advance, and to check whether or not a packet number that is included in the data packet from the other communication party (2, 1) is consistent with the packet number that is stored in the storage unit (106, 213), wherein in a case where the two packet numbers are consistent with each other, the control unit (120, 220) is arranged to generate a delivery acknowledgement including the packet number that is stored in the storage unit (106, 213), to transmit the generated delivery acknowledgement from the wireless communication unit (101, 201) to the other communication party (2, 1), and to update the packet number that is stored in the storage unit (106, 213), and wherein in a case where the two packet numbers are not consistent with each other, the control unit (120, 220) is arranged to generate a disconnection instruction to which a message urging activation of a packet service is added, and to transmit the generated disconnection instruction from the wireless communication unit (101, 201) to the other communication party (2, 1), wherein the message urging activation of the packet service causes the other communication party (2, 1) to rewrite a packet number stored in a storage unit (213, 106) of the other communication party (2, 1) as the initial value.