A downhole tool securing device and a frac plug which are excellent in setting properties and water pressure resistance and have excellent fracturing properties. A downhole tool securing device (slips) of a frac plug according to one embodiment of the present invention includes a button containing a powder metallurgy material and having a compressive elastic modulus of at least 13.5 GPa and a toughness of 0.23 GJ/m3 or greater and 1.0 GJ/m3 or less.