Provided are a meltblown nonwoven fabric including fibers containing a cyclic olefinic resin, and a production method thereof. The meltblown nonwoven fabric includes fibers containing a cyclic olefinic resin. Where an SEM image of the meltblown nonwoven fabric is taken in a magnification of 1,000； 100 points are randomly selected from the SEM image to obtain fiber diameter data； the obtained fiber diameter data are ordered from a smallest value to a largest value； and a target data in a range from a third quartile or larger are selected from the ordered data； the meltblown fabric has an average value of fiber diameter of equal to or less than 30 μm calculated from the target data.本發明提供一種由包含環狀烯烴系樹脂之纖維所構成的熔噴不織布、及熔噴不織布之製造方法。前述熔噴不織布為由包含環狀烯烴系樹脂之纖維所構成的熔噴不織布，其在放大1000倍的SEM影像中隨機選擇之100點纖維徑數據當中，具有大於從纖維徑較小的數據向纖維徑較大的數據將數據四等分所得之第3四分位數的纖維徑之數據的平均值為30μm以下。
