A LED filament and a LED filament bulb using the same are disclosed. The LED filament includes a carrier, a LED chip disposed on the carrier and a conductive lead connected to the carrier. The conductive lead is electrically connected to the LED chip and includes a lead head portion, a lead tail portion and a lead neck portion connecting the lead head portion with the lead tail portion. A solid body width of the lead neck portion is less than a maximum solid body width of the lead head portion. Because the lead neck portion with reduced solid body width can function as a vulnerable position of the conductive lead, when a stress is applied onto the conductive lead, the lead neck portion would first take action and therefore the bonding location between the lead head portion and the carrier or the carrier itself can be protected.