Is your dog under a year and a half? If so, he's probably just in that puppy "teething" stage that every dog runs through.
When our Pomeranian was a puppy he chewed EVERYTHING! You should see the rocker on one of our living room chairs!
Two things helped get this behavior under control. Giving him his own toys (a fuzzy red bone squeaky-toy is his favorite), and TIME! No longer a puppy, his chewing impulse is under control. But when he does feel the urge to chew, he turns to one of his MANY toys!
So...how old is your dog, and does he have his own toys? ALL DOGS chew when they're young, and need tons of supervision. Don't give him access to your valuables during this period. Give him plenty of loving supervision, firm but gentle correction, and HIS OWN TOYS!