A vaginal speculum comprising: an upper member having a first handle extending downwardly from the upper member; a lower member pivotally connected with the upper member and having a second handle extending downwardly from the lower member, located at a side of the first handle and having a first side surface away from the first handle and a second side surface near the first handle; and a positioning cavity formed in the second handle and having an insertion cavity recessed in the first side surface of the second handle and having an end surface away from the first side surface of the second handle spaced from the second side surface of the second handle and at least one cavity limiting surface defined in an annular surface of the insertion cavity; a threaded rod having a head mounted in the insertion cavity of the positioning cavity and having at least one head limiting surface defined in an annular surface of the head and corresponding to the at least one cavity limiting surface in position and shape; and a rod extending from the head toward the first handle and extending through the second handle and the first handle; and a nut connected with the rod of the threaded rod via a threaded connection and selectively abutting against the first handle; and characterized in that the positioning cavity has multiple engaging grooves arranged around the insertion cavity and spaced from each other, and each of the engaging grooves having a side opening formed in the annular surface of the insertion cavity and communicating with the insertion cavity and an end surface near the first side surface of the second handle spaced from the first side surface of the second handle; and the threaded rod has multiple engaging protrusions protruding from the annular surface of the head, spaced from each other, and respectively engaged with the engaging grooves of the positioning cavity. an upper member having a first handle extending downwardly from the upper member; a lower member pivotally connected with the upper member and having a second handle extending downwardly from the lower member, located at a side of the first handle and having a first side surface away from the first handle and a second side surface near the first handle; and a positioning cavity formed in the second handle and having an insertion cavity recessed in the first side surface of the second handle and having an end surface away from the first side surface of the second handle spaced from the second side surface of the second handle and at least one cavity limiting surface defined in an annular surface of the insertion cavity; a second handle extending downwardly from the lower member, located at a side of the first handle and having a first side surface away from the first handle and a second side surface near the first handle; and a positioning cavity formed in the second handle and having an insertion cavity recessed in the first side surface of the second handle and having an end surface away from the first side surface of the second handle spaced from the second side surface of the second handle and at least one cavity limiting surface defined in an annular surface of the insertion cavity; a threaded rod having a head mounted in the insertion cavity of the positioning cavity and having at least one head limiting surface defined in an annular surface of the head and corresponding to the at least one cavity limiting surface in position and shape; and a rod extending from the head toward the first handle and extending through the second handle and the first handle; and a head mounted in the insertion cavity of the positioning cavity and having at least one head limiting surface defined in an annular surface of the head and corresponding to the at least one cavity limiting surface in position and shape; and a rod extending from the head toward the first handle and extending through the second handle and the first handle; and a nut connected with the rod of the threaded rod via a threaded connection and selectively abutting against the first handle; and characterized in that the positioning cavity has multiple engaging grooves arranged around the insertion cavity and spaced from each other, and each of the engaging grooves having a side opening formed in the annular surface of the insertion cavity and communicating with the insertion cavity and an end surface near the first side surface of the second handle spaced from the first side surface of the second handle; and the threaded rod has multiple engaging protrusions protruding from the annular surface of the head, spaced from each other, and respectively engaged with the engaging grooves of the positioning cavity.