A composition for hard tissue repair comprising a monomer, a polymer powder and a polymerization initiator, wherein monomer is a (meth)acrylate-based monomer, the polymer powder is a mixture of a polymer powder (B-x) having an aspect ratio of 1.10 or more and a polymer powder (B-y) having an aspect ratio of 1.00 or more and less than 1.10, wherein polymer powder (B-x) and polymer powder (B-y) are each a (meth)acrylate-based polymer powder, and wherein with respect to the total amount of the polymer powder, the amount of the polymer powder (B-x) is 4.0 to 70% by mass, and the amount of the polymer powder (B-y) is 30 to 96.0% by mass, and the cumulative ratio of powder particles having aspect ratios of 1.00 or more and less than 1.10 in all of the powder particles contained in the composition for hard tissue repair is between 2.5 and 65 cumulative%, and wherein the aspect ratio is determined using the following method: i) a sample of polymer powder was dispersed in 2-propanol as a dispersing solvent and the sample was dispersed for 60 seconds in an ultrasonic bath with an output of 500 W; ii) the aspect ratio was measured using a dynamic image analysis method (wet method) using PITA-3 under the conditions of a sample liquid flow rate of 0.42 μL/sec, a carrier liquid flow rate of 416.67 μL/sec and an observation magnification (lens magnification) of 10 times; iii) the aspect ratio was then calculated using the following formula: Aspect ratio value = L / W L: major axis (maximum length, μm) W: short axis (length in the direction vertical to the maximum length, μm) and wherein the cumulative ratio of the powder particles having an aspect ratio of 1.00 or more and less than 1.10 was determined by plotting the distribution of aspect ratios of the powder particles on a graph and calculating the proportion of distribution in which the aspect ratio corresponds to the range of 1.00 or more and less than 1.10. monomer is a (meth)acrylate-based monomer, the polymer powder is a mixture of a polymer powder (B-x) having an aspect ratio of 1.10 or more and a polymer powder (B-y) having an aspect ratio of 1.00 or more and less than 1.10, wherein polymer powder (B-x) and polymer powder (B-y) are each a (meth)acrylate-based polymer powder, and wherein with respect to the total amount of the polymer powder, the amount of the polymer powder (B-x) is 4.0 to 70% by mass, and the amount of the polymer powder (B-y) is 30 to 96.0% by mass, and the cumulative ratio of powder particles having aspect ratios of 1.00 or more and less than 1.10 in all of the powder particles contained in the composition for hard tissue repair is between 2.5 and 65 cumulative%, and wherein the aspect ratio is determined using the following method: i) a sample of polymer powder was dispersed in 2-propanol as a dispersing solvent and the sample was dispersed for 60 seconds in an ultrasonic bath with an output of 500 W; ii) the aspect ratio was measured using a dynamic image analysis method (wet method) using PITA-3 under the conditions of a sample liquid flow rate of 0.42 μL/sec, a carrier liquid flow rate of 416.67 μL/sec and an observation magnification (lens magnification) of 10 times; iii) the aspect ratio was then calculated using the following formula: Aspect ratio value = L / W L: major axis (maximum length, μm) W: short axis (length in the direction vertical to the maximum length, μm) i) a sample of polymer powder was dispersed in 2-propanol as a dispersing solvent and the sample was dispersed for 60 seconds in an ultrasonic bath with an output of 500 W; ii) the aspect ratio was measured using a dynamic image analysis method (wet method) using PITA-3 under the conditions of a sample liquid flow rate of 0.42 μL/sec, a carrier liquid flow rate of 416.67 μL/sec and an observation magnification (lens magnification) of 10 times; iii) the aspect ratio was then calculated using the following formula: Aspect ratio value = L / W L: major axis (maximum length, μm) W: short axis (length in the direction vertical to the maximum length, μm) L: major axis (maximum length, μm) W: short axis (length in the direction vertical to the maximum length, μm)