A receiving device comprising: a variable gain amplifying unit varying its gain depending on a gain control value and operable to amplify an input analog signal; an analog-to-digital converting unit operable to convert an amplified analog signal output from the variable gain amplifying unit, into a digital signal; a digital signal judging unit operable to judge whether or not the digital signal output from the analog-to-digital converting unit is saturated; a preamble start detecting unit operable to detect, from the digital signal output from the analog-to-digital converting unit, a start of a section as a preamble signal which is attached to a head of a wireless packet signal; and a gain control unit operable to control a gain of the variable gain amplifying unit by calculating a gain value to be set in the variable gain amplifying unit in accordance with the digital signal output from the analog-to-digital converting unit and setting the calculated gain value in the variable gain amplifying unit; characterized in that the gain control unit controls the gain of the variable gain amplifying unit by performing a first gain control process in which the gain control unit repeatedly performs the calculation of the gain value to be set and the setting of the calculated gain value, during a first predetermined period, when the digital signal judging unit judges that the digital signal output from the analog-to-digital converting unit is saturated, and controls the gain of the variable gain amplifying unit by performing a second gain control process in which the gain control unit repeatedly performs the calculation of the gain value to be set and the setting of the calculated gain value, during a second predetermined period that is shorter than the first predetermined period, when the digital signal judging unit judges that the digital signal output from the analog-to-digital converting unit is not saturated, and the preamble start detecting unit detects the start of the section as the preamble signal. a variable gain amplifying unit varying its gain depending on a gain control value and operable to amplify an input analog signal; an analog-to-digital converting unit operable to convert an amplified analog signal output from the variable gain amplifying unit, into a digital signal; a digital signal judging unit operable to judge whether or not the digital signal output from the analog-to-digital converting unit is saturated; a preamble start detecting unit operable to detect, from the digital signal output from the analog-to-digital converting unit, a start of a section as a preamble signal which is attached to a head of a wireless packet signal; and a gain control unit operable to control a gain of the variable gain amplifying unit by calculating a gain value to be set in the variable gain amplifying unit in accordance with the digital signal output from the analog-to-digital converting unit and setting the calculated gain value in the variable gain amplifying unit; characterized in that the gain control unit controls the gain of the variable gain amplifying unit by performing a first gain control process in which the gain control unit repeatedly performs the calculation of the gain value to be set and the setting of the calculated gain value, during a first predetermined period, when the digital signal judging unit judges that the digital signal output from the analog-to-digital converting unit is saturated, and controls the gain of the variable gain amplifying unit by performing a second gain control process in which the gain control unit repeatedly performs the calculation of the gain value to be set and the setting of the calculated gain value, during a second predetermined period that is shorter than the first predetermined period, when the digital signal judging unit judges that the digital signal output from the analog-to-digital converting unit is not saturated, and the preamble start detecting unit detects the start of the section as the preamble signal.