Where is pcap_open() function? [C++][WinPcap]

Question

/* Open the device */
if ( (adhandle= pcap_open(d->name,
                          65536,
                          PCAP_OPENFLAG_PROMISCUOUS,
                          1000,
                          NULL,
                          errbuf)
   ) == NULL)
   {
        fprintf(stderr,"\nUnable to open the adapter. %s is not supported by WinPcap\n", d->name);
        /* Free the device list */
        pcap_freealldevs(alldevs);
        return -1;
   }

This code is in this.
I included pcap.h.
But I can't use pcap_open() function.
identifier "pcap_open" is undefined

Please help me.