A walker includes a front frame, a side frame, and a folding device. The front frame includes a sleeve having a positioning groove extending around a circumference of the front frame. The positioning groove has a deployment groove portion and a folding groove portion spaced apart from each other. The side frame has an inverted U shape and is rotatably disposed on the sleeve of the front frame. The side frame is changeable between a deployed position and a collapsed position. The folding device is disposed in the side frame. The folding device includes a pressing member that protrudes from the side frame, a folding strip that connects with the pressing member, and a latch that is laterally fixed to the folding strip. One end of the latch passes through the side frame and is movably disposed to the positioning groove of the front frame. The latch is driven by the pressing member to be selectively engaged with the folding groove portion or the deployment groove portion of the positioning groove to position the side frame.一種助行器，包含一前架、一側架，及一收合裝置。該前架包括一具有一繞其圓周延伸之定位槽的套管。該定位槽具有相間隔的一展開槽部及一收合槽部。該側架呈倒U形，並可轉動地設置在該前架的套管，且可在一展開位置及一收合位置之間改變。該收合裝置設置在該側架內，包括一部分突出該側架的按壓件、一連接該按壓件的收合條，及一橫向地固設在該收合條的插銷。該插銷一端部穿出該側架並可動地設置在該前架的定位槽。該插銷受該按壓件的帶動而可選擇地卡合於該定位槽的收合槽部或展開槽部，以定位該側架。
