A crane comprising: a main body portion which includes a lower travelling body and an upper slewing body turnably provided on the lower travelling body and to which a plurality of weights can be attached; a tag reader which is provided in the main body portion and acquires, from a weight tag mounted on each weight, identification data corresponding to each weight tag by radio communication; and a data processing device which acquires data from the tag reader, wherein the data processing device includes: a data acquisition portion which acquires the identification data characterised in that the acquisition portion acquires reception intensity data corresponding to each weight tag from the tag reader, the reception intensity data being indicative of a reception intensity of a signal in the radio communication between each weight tag and the tag reader; the data processing unit further includes: a data discrimination portion which discriminates the identification data corresponding to each weight tag into first identification data indicating that a reception intensity indicated by reception intensity data corresponding to the identification data exceeds a reference intensity set in advance for determining whether each weight is attached to the main body portion or not and other second identification data; an attachment determination portion which determines an attachment state of each weight to the main body portion based on the first identification data only; and a reference setting portion which sets the reference intensity in advance as a target to be compared with the reception intensity. a main body portion which includes a lower travelling body and an upper slewing body turnably provided on the lower travelling body and to which a plurality of weights can be attached; a tag reader which is provided in the main body portion and acquires, from a weight tag mounted on each weight, identification data corresponding to each weight tag by radio communication; and a data processing device which acquires data from the tag reader, wherein the data processing device includes: a data acquisition portion which acquires the identification data characterised in that the acquisition portion acquires reception intensity data corresponding to each weight tag from the tag reader, the reception intensity data being indicative of a reception intensity of a signal in the radio communication between each weight tag and the tag reader; the data processing unit further includes: a data discrimination portion which discriminates the identification data corresponding to each weight tag into first identification data indicating that a reception intensity indicated by reception intensity data corresponding to the identification data exceeds a reference intensity set in advance for determining whether each weight is attached to the main body portion or not and other second identification data; an attachment determination portion which determines an attachment state of each weight to the main body portion based on the first identification data only; and a reference setting portion which sets the reference intensity in advance as a target to be compared with the reception intensity. a data discrimination portion which discriminates the identification data corresponding to each weight tag into first identification data indicating that a reception intensity indicated by reception intensity data corresponding to the identification data exceeds a reference intensity set in advance for determining whether each weight is attached to the main body portion or not and other second identification data; an attachment determination portion which determines an attachment state of each weight to the main body portion based on the first identification data only; and a reference setting portion which sets the reference intensity in advance as a target to be compared with the reception intensity.