A height-adjusting device for shelves of appliances, in particular for dishwasher racks, comprising: a support member, defining a substantially planar surfaces having an upper edge and a lower edge and extending in a substantially vertical first plane, when in use; a locking element, having a proximal end, hinged with said support member at a first pivot axis that is normal to said first vertical plane and provided towards said lower edge, and a distal end having a pin that is operably linked via a biasing member to a second pivot axis vertically spaced apart from said first pivot axis towards said upper edge and that is normal to said first vertical plane, wherein said locking element is configured to move about said pivot axis relative to said support member between an engaged position and a disengaged position, opposite said engaged position relative to a second plane perpendicular to said first plane and containing said first pivot axis and said second pivot axis; a bracket member, slidably coupleable with said support member so as to allow vertical movement of said bracket member relative to said support member between a top position and a bottom position, comprising: a first cam surface, having at least one locking seat, configured to lockingly engage with said pin of said locking element when in said engaged position, when moving said bracket member from said top position towards said bottom position; a second cam surface, configured to operably engage with said pin of said locking element so as to move said locking element from said engaged position to said disengaged position and toggle said biasing member from a first biasing disposition, where said locking element is biased towards said first cam surface, to a second biasing disposition, where said locking element is biased away from said first cam surface, when moving said bracket member to said top position, and a third cam surface, configured to guidingly engage with said pin of said locking element so as to move said locking element from said disengaged position to said engaged position and toggle said biasing member from said second biasing disposition to said first biasing disposition, when moving said bracket member from said top position to said bottom position. a support member, defining a substantially planar surfaces having an upper edge and a lower edge and extending in a substantially vertical first plane, when in use; a locking element, having a proximal end, hinged with said support member at a first pivot axis that is normal to said first vertical plane and provided towards said lower edge, and a distal end having a pin that is operably linked via a biasing member to a second pivot axis vertically spaced apart from said first pivot axis towards said upper edge and that is normal to said first vertical plane, wherein said locking element is configured to move about said pivot axis relative to said support member between an engaged position and a disengaged position, opposite said engaged position relative to a second plane perpendicular to said first plane and containing said first pivot axis and said second pivot axis; a bracket member, slidably coupleable with said support member so as to allow vertical movement of said bracket member relative to said support member between a top position and a bottom position, comprising: a first cam surface, having at least one locking seat, configured to lockingly engage with said pin of said locking element when in said engaged position, when moving said bracket member from said top position towards said bottom position; a second cam surface, configured to operably engage with said pin of said locking element so as to move said locking element from said engaged position to said disengaged position and toggle said biasing member from a first biasing disposition, where said locking element is biased towards said first cam surface, to a second biasing disposition, where said locking element is biased away from said first cam surface, when moving said bracket member to said top position, and a third cam surface, configured to guidingly engage with said pin of said locking element so as to move said locking element from said disengaged position to said engaged position and toggle said biasing member from said second biasing disposition to said first biasing disposition, when moving said bracket member from said top position to said bottom position. a first cam surface, having at least one locking seat, configured to lockingly engage with said pin of said locking element when in said engaged position, when moving said bracket member from said top position towards said bottom position; a second cam surface, configured to operably engage with said pin of said locking element so as to move said locking element from said engaged position to said disengaged position and toggle said biasing member from a first biasing disposition, where said locking element is biased towards said first cam surface, to a second biasing disposition, where said locking element is biased away from said first cam surface, when moving said bracket member to said top position, and a third cam surface, configured to guidingly engage with said pin of said locking element so as to move said locking element from said disengaged position to said engaged position and toggle said biasing member from said second biasing disposition to said first biasing disposition, when moving said bracket member from said top position to said bottom position.