A flexible secondary battery includes an exterior member having an accommodation space inside, a cathode collector and an anode collector located in the accommodation space and spaced apart from each other, a cathode active material portion on the cathode collector, and an anode active material portion on the anode collector. The cathode collector includes a first connection portion extending in a first direction and a plurality of first leg portions protruding from the first connection portion in a second direction different from the first direction. The anode collector includes a second connection portion parallel to the first connection portion and a plurality of second leg portions protruding from the second connection portion toward the first connection portion. The first leg portions and the second leg portions are alternately arranged between the first connection portion and the second connection portion. The cathode active material portion is located only on the first leg portions. The anode active material portion is located on the second connection portion and the second leg portions.